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Resonant suppression of light transmission in high-refractive-index nanoparticle metasurfaces

Viktoriia Babicheva and Andrey Evlyukhin

Doc ID: 338711 Received 13 Jul 2018; Accepted 20 Sep 2018; Posted 20 Sep 2018  View: PDF

Abstract: High-refractive-index nanoparticle two-dimensional arrays have attracted a lot of interest recently as they support both electric and magnetic resonances and can be implemented as functional metasurfaces. Here we show that under particular conditions, the all-dielectric nanoparticle metasurfaces can resonantly suppress transmission. As an important example, resonant electric and magnetic dipole responses of silicon nanoparticle arrays are considered in the air as well in the dielectric matrix in visible and infrared spectral ranges. We show that the wave resonantly scattered forward by the one or both electric and magnetic dipole moments of nanoparticles can destructively interfere with the incident wave, providing significant suppression of the transmission through the array. The reported effect can find important applications in different fields related to optics and photonics such as the development of filters, sensors, and solar cell.

Sub-80 fs mode-locked Tm,Ho-codoped disordered garnet crystal oscillator operating at 2081 nm

Zhongben Pan, Yicheng Wang, Yongguang Zhao, Maciej Kowalczyk, Jaroslaw Sotor, Hualei Yuan, Yan Zhang, Xiaojun Dai, Huaqiang Cai, Ji Bae, Sun Young Choi, Fabian Rotermund, Pavel Loiko, Josep Maria Serres, Xavier Mateos, Uwe Griebner, and Valentin Petrov

Doc ID: 342416 Received 14 Aug 2018; Accepted 18 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: We demonstrate a mode-locked femtosecond laser based on the disordered garnet crystal Tm,Ho:CNGG. Employing a single-walled carbon nanotube saturable absorber, pulses as short as 83 fs and 76 fs at 2081 nm are achieved without and with external compression, respectively. The latter is, to our knowledge, the shortest pulse duration obtained from any Ho-doped or Tm,Ho-codoped laser. The average power amounts to 67 mW at a repetition rate of 102 MHz. By analyzing the soliton mode-locked regime the nonlinear refractive index of Tm,Ho:CNGG is estimated at 2081 nm and amounts to ~1.1 × 10-19 m2/W.

Deterministic generation of Greenberger-Horne-Zeilinger entangled states of cat-state qubits in circuit QED

Chui-Ping Yang and Zhen-Fei Zheng

Doc ID: 335464 Received 20 Jun 2018; Accepted 18 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: We propose an efficient method to generate a Greenberger-Horne-Zeilinger (GHZ) entangled state of three cat-state qubits (cqubits) via circuit QED. Inthis proposal, the GHZ state is prepared with three microwave cavities coupled to a superconducting transmon qutrit. Because the qutrit remains in the ground state during the operation, decoherence caused by the energy relaxation and dephasing of the qutrit is greatly suppressed. The GHZ state is created deterministically because no measurement on either the state of the coupler qutrit or the state of the cqubits is involved. Numerical simulations demonstrate that high-fidelity generation of a three-cqubit GHZ state is feasible with present circuit QED technology.

Enhancing the figure-of-merit of refractive index sensors by magnetoplasmons in nanogratings

Zhixiong Tang, Leyi Chen, Zhang Cheng, Shaoyin Zhang, Chengxin Lei, li yong, SIHAO WANG, Shaolong Tang, and Youwei Du

Doc ID: 341881 Received 08 Aug 2018; Accepted 18 Sep 2018; Posted 20 Sep 2018  View: PDF

Abstract: The sensing performance of one-dimensional magnetic nanograting based on magnetoplasmons was investigated. The predictable Kerr reversal and enhancement are achieved in our experiment. The further result shows that the shift of Kerr null point has a linear relationship with the surrounding refractive index in a wide range. And a huge figure of merit (FoM) of 1728/RIU is achieved, which is 1 order of magnitude higher than the results reported. The experiment and theory confirm that the excitation of surface plasmons leads to the Kerr reversal and enhancement, resulting in the huge FoM.

Pulse-regulated single-photon generation via quantum interference in a χ^(2) nonlinear nanocavity

Yuyi Yan, Yanbei Cheng, Shengguo Guan, Danying Yu, and zhenglu duan

Doc ID: 336406 Received 24 Jul 2018; Accepted 17 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: A scalable on-chip single-photon source at telecommunications wavelengths is an essential component of quantum communication networks. In this work, we numerically construct a pulse-regulated single-photon source based on an optical parametric amplifier in a nanocavity. Under conditions of pulsed excitation, we study the photon statistics of the source using the Monte Carlo wave-function method. The results show that there exits an optimum excitation pulse width for generating high-purity single photons, while the source brightness increases monotonically with increasing excitation pulse width.

Mid-infrared broadband superluminescent light emitter arrays

Jialin Sun, Chuncai Hou, jinchuan zhang, Ning Zhuo, hongmei chen, J. Q. Ning, Zhanguo Wang, Liu Fengqi, and Ziyang Zhang

Doc ID: 344269 Received 27 Aug 2018; Accepted 17 Sep 2018; Posted 18 Sep 2018  View: PDF

Abstract: Mid-infrared (MIR) room-temperature (RT) and continuous-wave (CW) broadband quantum cascade superluminescent light emitters (QCSLEs) have emerged as ideal broadband light sources for a number of applications of biomedical imaging, security inspection and gas detection. It is quite challenging to attain a RT-CW output power up to milliwatt level due to the very low efficiency of the spontaneous emission in the intersubband transitions in QCSLEs. In this work, for the first time, a compact light emitter array is realized by integrating several single emitters exhibiting a very high RT-CW power of 2.4 mW, which is attributed to the sufficient low reflectivity provided by the waveguide structure that including three sections with a short straight part adjacent to a tilted stripe and to a J-shaped waveguide, and the two-phonon resonance QC active structure. This advancement is certainly a big step forward to the applications of broadband light sources towards MIR photonics.

Interconversion between orbital and spin angular momentum of light beams in three-wave mixing processes in the bulk of isotropic chiral medium

Kirill Grigoriev, Vladimir Makarov, and Igor Perezhogin

Doc ID: 335840 Received 21 Jun 2018; Accepted 17 Sep 2018; Posted 20 Sep 2018  View: PDF

Abstract: Phenomenological description of nondegenerate and degenerate three-wave mixing in the bulk of isotropic chiral medium is given for the wide class of fundamental light beams with non-uniform polarization distribution and multimode transversal structure. Special attention is paid to the classical and quantum interpretation of interconversion between spin and orbital parts of angular momentum of the input and output beams.

Stimulated Two-Photon Emission in Bulk CdSe

Markus Betz, Stephan Melzer, Claudia Ruppert, and Alan Bristow

Doc ID: 338080 Received 06 Jul 2018; Accepted 17 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: While two-photon emission processes are firmly established in atomic physics, their observation and use in semiconductor physics remains elusive. Here we experimentally investigate stimulated two-photon emission in photoexcited bulk CdSe and identify requirements for the observation of stimulated two-photon emission. In particular, this process requires population inversion as well as two-photon transition energies close to the bandgap energy. In any regime investigated in the present study, net optical gain is not achieved as the free-carrier absorption intrinsically linked to the photoexcitation completely masks the two-photon gain. The results are well in line with a recent study on non-degenerate versions of two-photon emission in GaAs and place clear limits for the practical use of two-photon emission in optically excited semiconductors.

Null interferometric microscope for ICF-capsule surface-defect detection

Cong Wei, Jun Ma, Lei Chen, Jianxin Li, FAN CHEN, Rihong Zhu, Renhui Guo, Caojin Yuan, MENG JIE, Zongwei Wang, and GAO DANGZHONG

Doc ID: 335644 Received 20 Jun 2018; Accepted 17 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: Isolated defects on the surface of the inertial confinement fusion (ICF) capsule reduce the probability of ignition. Here, to the best of our knowledge, we present the first null interferometric microscope (NIM) for direct and large-field surface defects detection on ICF capsules. The planar reference mirror in conventional interferometric microscopes is replaced by a spherical reference mirror to achieve null interference in the full field of view (FOV). Further, via the use of a short-coherence light source system, parasitic fringes are avoided. The feasibility of the NIM is verified via experiments on a 0.7-mm-diameter capsule. A 1-mm diameter ICF capsule is also tested by the NIM to prove that the NIM has the ability to measure capsules with different diameters.

Au80Sn20-based targeted noncontact nanosoldering with low-power-consumption

Qiang Li, Ziyao Chen, XUAN ZHANG, Yong Peng, Pintu Ghosh, Guangnan Yao, Hao Luo, Jun Lu, and Min Qiu

Doc ID: 340241 Received 20 Jul 2018; Accepted 16 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: Energy-efficient nanosoldering technology for creating connections at the nanoscale is a long-sought-after goal for constructing advanced optoelectronic nanodevices. However, the ability to achieve noncontact, low power consumption, and targeted nanosoldering remains a challenge. In this work, we demonstrate a method of targeted photothermal nanosoldering of silver nanowires, which uses Au80Sn20 alloy nanowires as the nanosolder and a 532-nm continuous wave laser as the heat source. The required power for fusing the Au80Sn20 solder is reduced by a factor of 55 compared to the previously demonstrated Ag self-nanosolder case. Construction of a few typical nanostructures (including “X”, “Y” and “一” shaped junctions) are achieved with this method. Besides its low power consumption, it also provides advantages including noncontact and targeted soldering, thereby suggesting new avenues for fabricating complex nanostructures and advanced functional nanodevices.

Radiation-induced mismatch effect on performances of space chaos laser communication systems

Mi Li, Yifeng Hong, Su Wang, Yuejiang Song, and Xun Sun

Doc ID: 340799 Received 27 Jul 2018; Accepted 16 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: Chaotic modulation serves as an excellent scheme to enhance the confidentiality of space laser communication systems. Considering radiation and intensity scintillation, we establish bit error rate (BER) computation models for both an inter-satellite chaos laser communication system and a satellite-to-ground chaos laser communication system. Based on such models, numerical simulations are conducted to investigate the mismatch effect on the BER performance of these two typical systems. For an inter-satellite system, radiation can induce great parameter mismatches. For a satellite-to-ground system, the BER only slightly rises due to intensity scintillation being a more dominant deterioration effect than radiation. Our work has good reference value for the practical design of space chaos laser communication systems.

Fractal superconducting nanowire single-photon detectors with reduced polarization sensitivity

Xiaoming Chi, kai zou, Chao Gu, Julien Zichi, Yuhao Cheng, Nan Hu, Xiaojian Lan, Shufan Chen, Zuzeng Lin, Val Zwiller, and Xiaolong Hu

Doc ID: 341593 Received 06 Aug 2018; Accepted 16 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: We demonstrate the superconducting nanowire single-photon detectors (SNSPDs) based on a fractal design of the nanowires to reduce the polarization sensitivity of detection efficiency. We patterned niobium-titanium-nitride thin films into Peano curves with a line width of 100 nm and integrated the nanowires with optical micro-cavities to enhance their optical absorption. At the base temperature of 2.6 K, the fractal SNSPD exhibited a polarization-maximum device efficiency of 67% and a polarization-minimum device efficiency of 61%, at the wavelength of 1550 nm. Therefore, the polarization sensitivity, defined as their ratio, was 1.1, lower than the polarization sensitivity of the SNSPDs in the meander design. The reduced polarization sensitivity of the detector could be maintained for higher-order spatial modes in multi-mode optical fibers and could tolerate misalignment between the optical mode and the detector. This fractal design is applicable to both amorphous and polycrystalline materials that are commonly used for making SNSPDs.

Extending recordable time of light-in-flight recording by holography with double reference light pulses

Yu Sawashima, Daiki Yamanaka, Itsuki Takamoto, Atsushi Matsunaka, Yasuhiro Awatsuji, and Kenzo Nishio

Doc ID: 341557 Received 03 Aug 2018; Accepted 16 Sep 2018; Posted 20 Sep 2018  View: PDF

Abstract: Light-in-flight recording by holography is a powerful technique for observing ultrashort light pulse propagation. However, the recordable time of the technique has been limited by the lateral length of the holographic plate. Then, to extend the recordable time of light-in-flight recording by holography, we proposed a space-division multiplexing technique of holograms, which divides the holographic plate longitudinally and uses double reference light pulses. We experimentally demonstrated that the recordable time become twice as long as before for the first time using the proposed technique. Specifically, we recorded the motion picture of the ultrashort light pulse propagation for 6 ps.

Realization of a flat-band superprism on-chip from parallelogram lattice photonic crystals

Jeremy Upham, Boshen Gao, Liam O'Faolain, Zhimin Shi, Dr Sebastian Schulz, and Robert Boyd

Doc ID: 342451 Received 16 Aug 2018; Accepted 15 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: By optimizing the dispersion curve of a parallelogram-based 2D photonic crystal superprism for constant angular group velocity dispersion over a broad bandwidth, we designed a device capable of experimentally demonstrating linear dispersion from 1500 to 1600 nm with clear separation of as many as 8 channels, while maintaining a compact footprint.

High resolution air-clad imaging fibers

Harry Wood, Kerrianne Harrington, Tim Birks, Jonathan Knight, and James Stone

Doc ID: 335944 Received 25 Jun 2018; Accepted 15 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: We present a coherent fiber bundle comprising over 11,000 doped silica cores separated by an air-filled cladding. The fiber is characterized and its imaging quality is shown to be a substantial improvement over the commercial state of the art, with comparable resolution over an unparalleled spectral range.

Measurement error induced by the power-frequency delay of light source in optical correlation-domain distributed Brillouin sensors

Kwang Yong Song and Jae Ho Choi

Doc ID: 336550 Received 29 Jun 2018; Accepted 15 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: Direct current modulation of a semiconductor laser is a key method adopted in most of optical correlation-domain distributed Brillouin sensors such as Brillouin optical correlation domain analysis (BOCDA) and reflectometry (BOCDR) for localizing the sensing position by synthesis of optical coherence function. We report the distributed measurement of Brillouin frequency by the BOCDA or BOCDR system can suffer significant distortion caused by the relative delay between the output power and frequency variation of the modulated light source. We calculate the characteristics of the distortion by numerical simulations, and compare the results with experimental data obtained by a BOCDA system for the confirmation. Our results show that the maximum error of more than 30 MHz can occur in the Brillouin frequency measured under ordinary operating conditions with MHz-order direct current modulation.

Supercharge optical arrays

Bikashkali Midya, Wiktor Walasik, Natalia Litchinitser, and Liang Feng

Doc ID: 344693 Received 03 Sep 2018; Accepted 15 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: We introduce the notion of a supercharge optical array synthesized according to supersymmetric charge operators. Starting from an arbitrary array, mathematical supersymmetry transformation can be used systematically to create a zero-energy physical state below the ground state of the super-partner array. This zero-mode, which is pinned deep in the midgap of the corresponding supercharge array owing to the square-root spectral relationship between a supercharge and a super-Hamiltonian array, is shown to be protected because of the chiral symmetry inherent to a supercharge array. A supercharge array can be used in practical applications to design a waveguide array or a coupled resonators where the mid-gap zero-mode facilitates robust propagation of discretized light either in spatial or time domain.

Gas pressure dependence of microwave pulses generated by laser-produced filament plasmas

Alexander Englesbe, Jennifer Elle, Remington Reid, Adrian Lucero, Hugh Pohle, Matthew Domonkos, Serge Kalmykov, Karl Krushelnick, and Andreas Schmitt-Sody

Doc ID: 342613 Received 17 Aug 2018; Accepted 14 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: The plasma arising due to the propagation of a filamenting ultrafast laser pulse in air contains currents driven by the pulse that generate radiated electromagnetic fields. We report absolutely calibrated measurements of the frequency spectrum of microwaves radiated by the filament plasma from 2-40 GHz. The emission pattern of the electric field spectrum is mapped as a function of air pressure from atmosphere to 0.5 Torr. For fixed laser pulse energy, duration, and focal geometry we observe that decreasing the air pressure by a factor of approximately 10³ increases the amplitude of the electric field waveform by a factor of about 40. As the air pressure decreases, the lower frequency components (<10 GHz) increase in amplitude faster than those at higher frequencies (>20 GHz). This behavior has not been observed before, is not predicted by existing theory, and implies the existence of a radiation mechanism in the plasma distinct from that which emits at terahertz frequencies.

Compact Self-illuminated Image Up-conversion System-Based on Intra-cavity Second Harmonic Generation

Adrian Torregrosa, Haroldo Maestre Vicente, Maria Luisa Rico, and Juan Capmany

Doc ID: 341841 Received 09 Aug 2018; Accepted 14 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: We present an image up-conversion system based on intra-cavity Type II second harmonic generation to create an image in the visible spectrum of a target illuminated by an infrared laser. The system has the novelty of being self-illuminated. It uses some fractional leaking power of the infrared laser to illuminate a target located in the object focal plane of the system, and to couple back a created infrared target image to an intra-cavity nonlinear crystal, where it mixes with the cavity laser beam to obtain a second harmonic image, visible with a silicon CCD camera. For a proof of concept, we have built a system based on a diode-pumped Nd3+:YVO4 laser and an intra-cavity KTP crystal to up-convert 1342 nm target images to 671 nm. The up-converted power allowed us to capture real-time video in a standard non-intensified CCD camera, with 2.5 W of diode pump.

Integrated broadband dual-polarization Ge-rich SiGe mid-infrared Fourier-Transform spectrometer

Qiankun Liu, Joan Manel Ramirez, Vladyslav Vakarin, Xavier LE ROUX, Carlos Alonso-Ramos, Jacopo Frigerio, Andrea Ballabio, Enrico Talamas, David Bouville, Laurent Vivien, Giovanni Isella, and Delphine Marris-Morini

Doc ID: 342759 Received 22 Aug 2018; Accepted 14 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: Miniaturized on-chip spectrometers covering a wide band of the mid-infrared spectrum have an immense potential for multi-target detection in high-impact applications like chemical sensing or environmental monitoring. Specifically, multi-aperture spatial heterodyne Fourier transform spectrometers (SHFTS) provide high throughput and improved tolerances against fabrication errors, compared to conventional counterparts. Still, state-of-the-art implementations have only shown single polarization operation in narrow bandwidths within the near and short infrared. Here, we demonstrate the first dual-polarization ultra wideband SHFTS working beyond 5 µm wavelength. We exploit the unique flexibility in material engineering of the graded-index germanium-rich silicon-germanium (Ge-rich SiGe) photonic platform to implement a SHFTS with experimental resolution better than 15 cm-1 for both orthogonal polarizations in an unprecedented bandwidth of 800 cm-1 (5-8.5 µm wavelength).

Color domains in fiber lasers

Georges Semaan, yichang meng, Meriem Kemel, Mohamed Salhi, Andrey Komarov, and Francois Sanchez

Doc ID: 341852 Received 09 Aug 2018; Accepted 14 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: We report on the experimental observation of a color domain (CD) phenomenon in dissipative soliton fiber laser. The CDs are constituted by wavelength-dependent condensed soliton phase. Single color domain (SCD), dual color domain (DCD) and tricolor domain (TCD) that occupy all the cavity space are observed. The CDs have flexible tunability of duty cycle, amplitude, wavelength and wavelength spacing. The CDs derive from the wavelength-dependent slow evolution of gain, and the formation mechanism of multiple CDs can be explained by cross gain saturation (XGS).

Switchable Pancharatnam-Berry microlens array with nano-imprinted liquid crystal alignment

Ziqian He, Yun-Han Lee, Ran Chen, Debashis Chanda, and Shin-Tson Wu

Doc ID: 340679 Received 30 Jul 2018; Accepted 14 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: We report a rapid nano-imprinting technique to pattern the liquid crystal alignment of a Pancharatnam-Berry phase microlens array. Through implementing a single-side aligned cell, we demonstrate a switchable microlens array with fast response time and low operation voltage. Further investigation of focusing property as well as imaging capability ensure the good quality of the microlens array. Besides planar structures, this method is also promising for patterning liquid crystal alignment on curvilinear surfaces.

Multi-aperture snapshot compressive hyperspectral camera

Yaniv oiknine, Yitzhak August, and Adrian Stern

Doc ID: 341972 Received 09 Aug 2018; Accepted 13 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: In this Letter, we present a new snapshot hyperspectral (HS) camera based on a multi-aperture design. The technique uses an array of modified Fabry–Perot resonators (mFPRs) together with a lens array in order to acquire an array of spectrally multiplexed modulated sub-images. Then, the original HS image is reconstructed using a compressive sensing (CS) reconstruction algorithm. The HS camera has high optical throughput and enables acquisition of almost gigapixel HS datacubes with hundreds of spectral bands. Using our camera, we demonstrate optically compression of approximately 37:1.

Fiber-based 920 nm femtosecond laser for two-photon microscopy

Charles-Henri Hage, Jean-Thomas Gomes, Sylvia Bardet, Geoffroy Granger, Mathieu Jossent, Laure Lavoute, Dmitry Gaponov, and Sebastien Fevrier

Doc ID: 340343 Received 23 Jul 2018; Accepted 13 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: We introduce a fiber-based laser system providing 130 fs pulses with 3.5 nJ energy at 920 nm at a 43 MHz repetition rate and illustrate the potential of the source for two-photon excited fluorescence microscopy of living mouse brain. The laser source is based on frequency-doubling high-energy solitons generated and frequency-shifted to 1840 nm in large mode area fibers. This simple laser system could unleash the potential of two-photon microscopy techniques in the biology laboratory where green fluorescent proteins with emission spectrum peaking around 920 nm are used in routine.

Spectrally efficient digital mobile fronthaul with discrete cosine transform and multi-band quantization

xiang li, Li Haibo, Ming Luo, and shaohua yu

Doc ID: 340500 Received 24 Jul 2018; Accepted 13 Sep 2018; Posted 17 Sep 2018  View: PDF

Abstract: A spectrally efficient digital mobile fronthaul with discrete cosine transform (DCT) and multi-band quantization is firstly proposed and experimentally demonstrated. In this approach, the baseband OFDM symbols are segmented into individual blocks and independently transformed by DCT to obtain a set of transform coefficients. Due to the strong energy compaction property of DCT, most of the signal information tends to be concentrated in some parts of the transform coefficients. Different from digitizing each OFDM sample with the same number of quantization bits (QBs) in previous digital mobile fronthaul, multi-band quantization (MBQ) is introduced to separately digitize different parts of the coefficients with different number of quantization bits according to the significance of these coefficients. Furthermore, the part of transform coefficients with very little significance is discarded. Thus, the total number of required QBs for digitizing an OFDM symbol can be greatly reduced, thereby high bandwidth efficiency can be achieved. In the experiment, the proposed DCT-MBQ based digital mobile fronthaul transmission is demonstrated over a 25-Gb/s PAM-4 intensity modulation-direct detection optical link supporting up to 61 x 20-MHz 5G-NR carriers with 1024-QAM, achieving an EVM of 0.65%. The equivalent CPRI rates from 55 to 157 Gb/s are supported.

Fabrication techniques for mid-IR resonant devices

Robert Magnusson and Daniel Carney

Doc ID: 341320 Received 01 Aug 2018; Accepted 13 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: Photonic metastructures operating in the 8 to 13 μm mid-IR are fast becoming a topic of active research. However, literature describing techniques for their fabrication which lies on a scale that falls between nanofabrication and MEMS technology is scant. Here, we present detailed fabrication blueprints for achieving robust and repeatable results for devices in this region. Applying a Ge device layer on a ZnS substrate, we fabricate a materially-robust TM-polarized wideband reflector with a high reflectance in a 2.4 μm band. We then regrow a conformal layer on the device boosting its performance to yield a~3 μm 90% reflectance band from 8.1 to 11.1 μm and a band of 98% reflectance spanning 8.7 to 10.4 μm. The generalized methods presented are applicable in most labs with ordinary fabrication resources.

Self-calibrating and high-sensitivity microwave phase noise analyzer applying optical frequency comb generator and optical-hybrid-based I/Q detector

Shilong Pan, Jingzhan Shi, Fangzheng Zhang, Yu Zhang, De Ben, and Lijun Sun

Doc ID: 342669 Received 20 Aug 2018; Accepted 13 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: Phase noise analyzer (PNA) is indispensable for evaluating the short-term stability of microwave signals. In this Letter, a high-sensitivity PNA with self-calibration capability is proposed based on an optical frequency comb generator and an optical-hybrid-based I/Q detector. The negative factors that result in inaccurate measurement, including the direct component interference, amplitude noises of the microwave signal under test and the laser, and phase noise of the laser, are all eliminated through digital signal processing. A proof-of-concept experiment is performed. The established PNA can achieve accurate phase noise measurement with a high-sensitivity of -146.1 dBc/Hz@10 kHz, and self-calibrating property of the PNA is also verified.

Impact of dipolar clusters on electro-optic effects in KTa1-xNbxO3 crystal

Peng Tan, Hao Tian, Yu Wang, xiangda meng, Fei Huang, Xilong Cao, Chengpeng Hu, Li Li, and Zhongxiang Zhou

Doc ID: 342797 Received 27 Aug 2018; Accepted 13 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: Dipolar clusters are crucial structure factors in electro-optic (EO) effects. Here, the impacts of dipolar clusters on EO effects are investigated in KTa1–xNbxO3 using the electric-field-dependent EO characteristics. The results indicate that the field-driven reorientation of dipolar clusters determines the orientational electric susceptibility, deeply contributing to the excellent quadratic EO effects. The controlled average size of correlated local dipoles and uniform orientation of ferroelectric domains efficiently suppress light scattering, being beneficial for the modulation of incident light. The understanding of dipolar clusters-triggered EO responses is valuable for exploring origins of large EO effects and optimizing EO properties of materials.

Phase sensitivity of off-axis digital holography

Shichao Chen, Chengshuai Li, Cheng Ma, Ting-Chung Poon, and Yizheng Zhu

Doc ID: 335300 Received 15 Jun 2018; Accepted 13 Sep 2018; Posted 13 Sep 2018  View: PDF

Abstract: In off-axis digital holography, the Fourier transform-based algorithm is commonly used for signal processing. Here, we derive the theoretical phase sensitivity of this algorithm, which can be calculated from a single 2D hologram. This algorithm sensitivity represents the best achievable sensitivity of a system using this algorithm. Our derivation treats the signal in its most general form, considering non-uniform illumination and the effect of sideband filtering. As a result, the phase sensitivity varies spatially, determined by local signal-to-noise ratio. Sensitivity expressions for both shot noise and uniform noise models are given. These results are validated with simulations and experiments. Significantly, this theoretical sensitivity can serve as a baseline metric for assessing the performance of a phase imaging system, such as experimental sensitivity and hardware stability, which are critical for high-sensitivity quantitative phase imaging. In addition, the results are equally applicable to other interferometric techniques with similar interferogram patterns and signal processing algorithms.

Terahertz microscopy assisted by semiconductor nonlinearities

Francois Blanchard, XIN CHAI, Tomoko Tanaka, Takashi Arikawa, Tsuneyuki Ozaki, Roberto Morandotti, and Koichiro Tanaka

Doc ID: 335308 Received 27 Jun 2018; Accepted 13 Sep 2018; Posted 13 Sep 2018  View: PDF

Abstract: Terahertz (THz) imaging 
is currently based on linear effects, but there is great interest on how nonlinear effects induced by terahertz radiation could be exploited to provide extra information that is unobtainable by conventional imaging schemes. In particular, at field strengths on the order of 100 kV cm–1 to 1 MV cm–1, transmission properties inside semiconductor materials are largely affected at the picosecond time-scale, which raise the prospect of interesting nonlinear imaging applications at THz frequencies. Here, we experimentally investigate a method to map the two-dimensional nonlinear near-field distribution of an intense THz pulse passing through a thin film doped semiconductor. By inserting a metamaterial structure between the electro optic sensor and the doped film, the nonlinear near-field dynamics shows a different and enhanced contrast of the sample when compared to its linear counterpart.

Light scattering by pulmonary alveoli and airway surface liquid using a concentric sphere model

Kristen Maitland, Madeleine Durkee, Grace Fletcher, Camella Carlson, Kanci Matheson, Sarah Swift, Jeffrey Cirillo, and Duncan Maitland

Doc ID: 336397 Received 02 Jul 2018; Accepted 12 Sep 2018; Posted 13 Sep 2018  View: PDF

Abstract: We employ a concentric sphere Mie scattering model to describe light scattering by pulmonary alveoli and the airway surface liquid (ASL). Using this layered sphere model, we compare alveolar scattering at different points along the respiratory cycle and observe the effect of ASL thickness on light scattering within the lung. We have also extrapolated the model to investigate alveolar scattering in different animal models of pulmonary disease. This model of pulmonary light scattering can estimate in vivo optical properties for normal and pathological states, potentially aiding the design of optical imaging systems for diagnosis and investigation of pulmonary pathologies.

Supercontinuum Spectral-domain Ghost Imaging

Goëry Genty, Caroline Amiot, Piotr Ryczkowski, Ari Tapio Friberg, and John Dudley

Doc ID: 339943 Received 17 Jul 2018; Accepted 12 Sep 2018; Posted 12 Sep 2018  View: PDF

Abstract: Ghost imaging is a technique that generates high-resolution images by correlating the intensity of two light beams, neither of which independently contains useful information about the shape of the object. Ghost imaging has been demonstrated in both the spatial and temporal domains, using incoherent classical light sources or entangled photon pairs. Here, we exploit recent progress in ultrafast real-time measurement techniques to demonstrate ultrafast, scan-free, ghost imaging in the frequency domain using a continuous spectrum from an incoherent supercontinuum light source with random spectral fluctuations. We demonstrate the application of this technique to broadband spectroscopic measurements of methane absorption performed with sub-nm resolution. Our results offer novel perspectives for remote sensing in low light conditions, or in spectral regions where sensitive detectors are lacking.

Discovery of Parabolic Microresonators Produced via Fiber Tapering

Misha Sumetsky, Dashiell Vitullo, Gabriella Gardosi, Sajid Zaki, Kirill Tokmakov, and Michael Brodsky

Doc ID: 341669 Received 06 Aug 2018; Accepted 12 Sep 2018; Posted 12 Sep 2018  View: PDF

Abstract: We demonstrate a new method for creation of SNAP microresonators with harmonic profiles via fiber taperingin a laser-heated microfurnace. The simple proceduremakes microresonators that support hundredsof axial modes with good spacing uniformity, yieldinga promising prospective method for fabricating miniaturefrequency comb generators and dispersionless delaylines.

Sensitive Real-Time Monitoring of Refractive Indexes and Components Using Microstructure Optical FiberMicrofluidic

Boyao Li, Zicheng Sheng, Meng Wu, Xinyu Liu, Guiyao Zhou, Jiantao Liu, Zhiyun Hou, and ming xia

Doc ID: 341968 Received 10 Aug 2018; Accepted 12 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: Based on the surface plasmon resonance of metal and anti-resonance principles of hole-core microstructure optical fiber (MSF), in this paper, we demonstrated a microstructure optical fiber microfluidic that combines silver film and hole-core MSF to achieve the sensitive real-time monitoring of refractive indexes and components. The large hole core is common channel for guiding light and flowingmeasuredliquid. Because of interaction between light and continuous flow measured liquid, the component and refractive index can be simultaneously monitored by the characteristic absorption wavelength and the surface plasmon resonant peak position respectively. These results indicate that microstructure optical fiber microfluidic is an ideal multi-parameter measurement optical sensor.

Room temperature Fe2+:Cd1-xMnxTe laser generating at 5.4 – 6 μm

Michal Jelinek, Maxim Doroshenko, Helena Jelinkova, Jan Sulc, David Vyhlídal, Nazar Kovalenko, and Igor Terzin

Doc ID: 341631 Received 06 Aug 2018; Accepted 11 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: Six-μm laser generation at room temperature was achieved from Fe2+-doped Cd1-xMnxTe solid-solution active media for the first time. Laser properties of Fe2+:Cd1-xMnxTe crystals with a various concentration of manganese Mn (x = 0.1, 0.52, 0.56, 0.68, and 0.76) were investigated. The increase of Mn content in these crystals was shown to result in an almost similar long-wavelength shift of absorption, fluorescence, and laser output spectra of about ~60 nm per each 10 % of Mn. The laser generation was achieved in all crystals with the maximum output energies up to 30 μJ (for x = 0.52). The laser central oscillation wavelength is significantly influenced by Mn concentration and vary in the range from 5400 nm up to 6000 nm.

Broadband cantilever-enhanced photoacoustic spectroscopy in the mid-IR using supercontinuum

Goëry Genty, Tommi Mikkonen, Caroline Amiot, Antti Aalto, Kim Patokoski, and Juha Toivonen

Doc ID: 337787 Received 04 Jul 2018; Accepted 10 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: We demonstrate cantilever-enhanced photoacoustic spectroscopy in the mid-infrared using a supercontin- uum source. The approach is broadband, compact, and allows for higher photoacoustic signal intensity and en- hanced signal-to-noise ratio as compared to systems em- ploying conventional back body radiation sources. Us- ing this technique, we perform spectroscopic measure- ments of the full ro-vibrational band structure of water vapor at 1900 nm and methane at 3300 nm with relative signal enhancement factors of 70 and 19, respectively, when compared to measurements that use a black body radiation source. Our results offer novel perspective for photoacoustic detection opening the door to compact and sensitive broadband analyzers in the mid-infrared spectral region.

Counter-propagating modes in a Fabry-Pérot-type resonator

Markus Pollnau

Doc ID: 338099 Received 06 Jul 2018; Accepted 10 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: The longitudinal optical modes of a Fabry-Pérot resonator are investigated. We consider (i) the three- and one-dimensional spectral mode density in free space and in standing-wave resonators, (ii) the infinite sum of mode profiles, resulting in the Airy distribution, (iii) the comparison between a two-mirror resonator and an infinite periodic lensguide, and (iv) the comparison between a two-mirror resonator and a ring resonator. It is consistently deduced that the two counter-propagating waves with wave vectors ±|kq| at the same resonance frequency νq and polarization constitute independent optical modes with mode indices ±|q|.

Temperature and excitation wavelength-dependent photoluminescence of CH3NH3PbBr3 crystal

Wenzhi Wu and Qi Wang

Doc ID: 339839 Received 06 Aug 2018; Accepted 10 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: We have investigated temperature and excitation wavelength-dependent luminescent properties of CH3NH3PbBr3 (MAPbBr3) perovskite crystal using steady-state and time-resolved photoluminescence (PL) spectroscopy. Optical spectroscopic results indicate that the PL intensity, peak wavelength and the full width of half maximum (FWHM) are jumped due to phase transitions from orthorhombic to tetragonal and cubic phase. As temperature increases the peaks of above-bandgap and intrinsic PL have blueshift and redshift, respectively. The above-bandgap PL emerges under one-photon laser excitation, and vanishes under the excitation of near-infrared femtosecond laser due to reabsorption. The initial redshift of PL peak and PL lifetime change at various wavelengths reveals the existence of a trap-assisted excitonic state. It is found that upconversion PL in all phases is composed of a photoinduced thermal-assisted and an intrinsic excitonic state, which produces the observation of biexponential dynamics. Our results can facilitate the further understanding of the thermal effect of excitonic recombination in hybrid perovskite crystal.

Fabrication and properties of broadband antireflective film on inert perfluoropolymer induced by inductively coupled oxygen plasma

Shufan Chen, laixi sun, Fan Yang, Ye Xin, Jiang Xiaodong, and Weidong Wu

Doc ID: 340430 Received 25 Jul 2018; Accepted 10 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: Fluorinated ethylene propylene (FEP) film is an attractive candidate for mitigating target-debris in high power laser systems due to its remarkable advantages such as low cost, low absorption, and high damage threshold. However, the inert surface with bad wettability present an enormous challenge to realize optical antireflection. In this Letter, we experimentally demonstrate broadband antireflection of FEP film can be achieved through combining oxygen plasma treatment and sol-gel coating techniques. By optimizing the plasma treating time and withdrawal rate during the coating process, the treated FEP film has a 4.7% enhanced transmittance comparing to the untreated sample. In the case, transmittance over 99% with wide wave band ranging from 600 to 950 nm is achieved. The mechanism of broadband antireflection was revealed by investigating the fluorocarbon groups on FEP surface. The applicable wave band of antireflective FEP film can be designed at will by changing plasma treating conditions, which could open up a new avenue in the field of laser debris mitigation.

On the Hamiltonian form of the cross mode modulationin nonlinear optical waveguides

Jing Xu, Haofan Yang, Weijin Chen, Hanwen Hu, Yuntian Chen, and Xinliang Zhang

Doc ID: 341005 Received 30 Jul 2018; Accepted 10 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: It is commonly believed that the Hamiltonian approach only applies to linear systems, or nonlinear systems with proper linearization procedures. In this paper, we show that the the Hamiltonian approach based on linear coupled mode theory applies excellently well for the cross mode modulation (XMM), i.e., the field variation of the probe light induced by a strong co-propagating pump light in a degenerate mode-group. By deriving the eigenvalues and eigenvectors of the nonlinear system, the evolution of the probe light can be obtained, which agrees with the numerical simulations of the multimode nonlinear Schrödinger equations. Using the Hamiltonian approach, a simple approach for determining the pump mode for realizingarbitrary mode conversion is discussed. Two concrete scenarios of the optically-induced vector mode conversions within the LP₁₁-mode group are further exemplified.

A lock-in white-light interferometry based all-optical photoacoustic spectrometer

Ke Chen, Zhihao Yu, Zhenfeng Gong, and Qingxu Yu

Doc ID: 332723 Received 27 May 2018; Accepted 10 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: An all-optical photoacoustic spectroscopy (PAS) based on lock-in white-light interferometry (WLI) is proposed for trace gas detection. The cavity length of the fiber-optic Fabry-Perot cantilever microphone is demodulated by a high-speed white-light interferometer, whose spectral sampling is synchronously triggered by a phased locked signal. To improve the signal-to-noise ratio (SNR), the demodulated digital photoacoustic signal is further processed by a specially designed virtual lock-in amplifier. The designed photoacoustic spectrometer has been tested for trace acetylene (C2H2) detection in the near-infrared region. With 1 W excitation power and 200 s averaging time, the detection limit (1σ) is estimated to be 71 ppt.

Real-time characterization of optical soliton molecule dynamics in an ultrafast thulium fiber laser

Saïd Hamdi, Aurelien Coillet, and Philippe Grelu

Doc ID: 338690 Received 13 Jul 2018; Accepted 10 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: We present an experimental characterization of the internal oscillations, vibrations and transients of optical soliton molecules generated in a passively mode-locked thulium-doped fiber laser. We use custom linearly-chirped Bragg grating filters to perform real-time spectral measurement of the ultrafast dynamics at wavelengths around 2 µm.

Off-axis core transmission characteristics of helically twisted photonic crystal fibers

Takeshi Fujisawa and Kunimasa Saitoh

Doc ID: 342650 Received 17 Aug 2018; Accepted 10 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: Transmission characteristics of helically twisted photonic crystal fibers (PCFs) having off-axis cores are theoretically investigated for the first time. Due to the modified equivalent permittivity and permeability tensors induced by helical twisting, the transmission characteristics of helically twisted PCF depend on the core position. A beam propagation method developed for helically twisted waveguides, which explained the reported transmission spectra of helically twisted PCFs both qualitatively and quantitatively, is used for the analysis. The loss is significantly increased for shorter wavelength side, if the position of the core is far from the rotation axis, due to the coupling to twist-induced cladding modes. On the other hand, for longer wavelength side, the loss of one of the components of circularly polarized light is increased, namely, input linearly polarized light becomes close to left- or right-circularly polarized light depending on the rotation direction. These results indicate that helically twisted PCFs with off-axis core can be used for core-position-dependent polarization controlling devices.

Photonic potential for TM waves

Alessandro Alberucci, Jisha Pannian, and Stefan Nolte

Doc ID: 341401 Received 01 Aug 2018; Accepted 10 Sep 2018; Posted 13 Sep 2018  View: PDF

Abstract: We discuss the effective photonic potential for TM waves in inhomogeneous isotropic media. The model provides an easy and intuitive comprehension of form birefringence, paving the way for a new approach on the design of graded-index optical waveguides on nanometric scales. We investigate the application to nanophotonic devices, including integrated nanoscale wave plates and slot waveguides.

Broadband multicolor upconversion from Mn2+-Yb3+ codoped fluorosilicate glasses and transparent glass ceramics

Xin Wang, Yushi Chu, Zhiyong Yang, Ke Tian, Wenhao li, Shunbin Wang, Shijie Jia, Gerald Farrell, Gilberto Brambilla, and Pengfei Wang

Doc ID: 340807 Received 06 Aug 2018; Accepted 10 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: In contrast to well-known upconversion (UC) emission from Yb3+-Mn2+ co-doped crystal, a room-temperature intense broadband UC phenomenon was first observed both in Yb3+-Mn2+ co-doped fluorosilicate glasses and transparent glass ceramics under 980 nm pumping. The obtained photoluminescence (PL) ranged from yellow to white to blue. We attributed this effect to the cooperative UC of Yb3+ and to the formation of Yb3+-Mn2+ pairs. After heat treatment, KZnF3 nanocrystals appeared in the glass matrix, as identified by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the emission intensity increased 45 times. We believe that Yb3+-Mn2+ co-doped glasses or glass ceramics show great potential as a material for multi-color displays.

Experimental and numerical characterisation of an all-fibre laser with saturable absorber

Robert Otupiri, Bruno Garbin, Bernd Krauskopf, and Neil Broderick

Doc ID: 341419 Received 02 Aug 2018; Accepted 09 Sep 2018; Posted 14 Sep 2018  View: PDF

Abstract: We experimentally characterise the pulsing dynamics of a short all-fibre laser consisting of separate gain and absorber sections. Systematically varying the optical pump power for different lengths of the absorber section (ranging from 0.21m to 1.48 m), allows us to map out the qualitative behaviour of the system. This identifies three main operational regions: non-lasing, stable Q-switching and irregular pulsing. When interpreted in terms of the bifurcation structure of the Yamada model, the experimental results are in good qualitative agreement.

Photonic millimeter-wave ultra-wideband signal generation using frequency up-conversion based on stimulated Brillouin scattering effect

cong du, Weinan Zhou, yue wang, Minghai Wang, di wang, Kongjia Wang, Wei Dong, and Xin Zhang

Doc ID: 340387 Received 23 Jul 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: We present a novel and simple scheme for photonic generation of millimeter-wave (MMW) ultra-wideband (UWB) signal free of low-frequency component, which is implemented by using a stimulated Brillouin scattering (SBS)-based frequency doubling method. A dual-parallel Mach-Zehnder modulator (DPMZM) is incorporated to generate appropriate optical sidebands and an optical carrier carrying the UWB signal. Then, the single-sideband (SSB) modulation is realized based on the successive SBS frequency shifting process. Eventually, a UWB signal is up-converted to twice the frequency of the radio frequency (RF) signal. To vindicate the feasibility of the proposed scheme, an experiment is carried out and it turns out that a UWB signal with bandwidth of 7 GHz is up-converted to 21.75 GHz. The spectrum of the generated signal meets well with the Federal Communication Committee (FCC) mask.

Hybrid integration of an evanescently coupled AlGaAs micro-disk resonator with a silicon waveguide by nanoscale-accurate transfer printing

Benoit Guilhabert, John McPhillimy, Stuart May, Charalambos Klitis, Martin D. Dawson, Marc Sorel, and Michael Strain

Doc ID: 338393 Received 24 Jul 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Hybrid integration of a III-V micro-disk resonator on a silicon-on-insulator waveguide platform is demonstrated. Transfer printing with nanoscale accuracy is used to micro-assemble an evanescently coupled all-pass micro-disk resonator, with a targeted coupler gap of 100 nm using pre-fabricated AlGaAs and silicon components. Transmission measurements show hybrid resonances with a loaded Q-factor of 7x10³ and cavity finesse of over 100.

Highly-uniform resonator-based visible spectrometer on a Si₃N₄ platform with robust and accurate post-fabrication trimming

Tianren Fan, Zhixuan Xia, Ali Adibi, and Ali Asghar Eftekhar

Doc ID: 341102 Received 01 Aug 2018; Accepted 09 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: A resonator array-based spectrometer for visible/near-infrared (NIR) wavelengths is fabricated on a low-loss silicon nitride (Si₃N₄) material platform. Ideally, a spectrometer should uniformly sample the input spectrum. However, resonator-based spectrometers, in which each spectral sample corresponds to resonance wavelength of one of the resonators in the array, suffer from wavelength sampling non-uniformity caused by the high sensitivity of the resonant wavelengths of different resonators to the dimensional variations caused by fabrication imperfections. Using an alignment-insensitive post-fabrication trimming technique, we reduce the standard deviation (STD) of resonance wavelength of a 60-channel integrated photonic spectrometer in Si₃N₄ to a record low value of 5 pm in the visible wavelength range. This approach can be used to realize wideband and uniform visible spectrometers that are desirable for applications such as optical signal processing and biological sensing.

Active control of light slowing enabled by couplingelectromagnetic metamaterials with low-lossygraphene

Junwei Chen, Xiaowen Li, Xi Shi, Chenfang Fan, M Tuhtasun, Xiaoyong He, wangzhou Shi, and Feng Liu

Doc ID: 341229 Received 31 Jul 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: We theoretically investigate the dynamical control oflight slowing within the induced transparent window,e.g., in near–infrared frequencies, in EIT metamaterialsloaded by low-lossy graphene. The coupling withgraphene enables distinctive optical responses of the‘bright’ and ‘dark’ resonators in EIT metamaterials, renderinga switching of the transparent window and amodulation on the light dispersion. The optical performanceof the transparent window manifests continuoustuning as graphene doping level changes. We showthe active modulation on the optical properties of thetransparent window enabled by low-lossy graphene isdistinctive with either the passive way via adjusting theinterspacing between the building blocks of EIT metamaterials,or the active tuning by high-lossy graphene.Furthermore, we report that the group refractive indexcan be in situ tuned dynamically over a broad range,e.g., 2 orders for near-infrared frequencies, togetherwith the absorption maintaining at the similar levelwith that of the unloaded structure. Our study offersnew possibilities towards chip-scale devices such as activeoptical switching, filtering, and data storing.

Frequency-locked cavity ring-down Faraday rotation spectroscopy

Jakob Hayden, Jonas Westberg, Charles Patrick, Bernhard Lendl, and Gerard Wysocki

Doc ID: 342305 Received 14 Aug 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Cavity ring-down Faraday rotation spectroscopy (CRD-FRS) is a technique for trace gas measurements of paramagnetic species that retrieves the molecular concentration from the polarization rotation measured as the difference between simultaneously recorded ring-down times of two orthogonal polarization states. The differential measurement is inherently insensitive to non-absorber related losses, which makes off-resonance measurements redundant. We exploit this unique property by actively line-locking to a molecular transition for calibration-free trace gas concentration retrieval. In addition, we enhance the effective duty-cycle of the system by implementing a Pound-Drever-Hall laser lock to the cavity resonance, which allows for ring-down rates of up to 9 kHz. The system performance is demonstrated by measurements of trace oxygen with a minimum detection limit at the ppmv/√Hz-level.

Dynamics of femtosecond laser induced shockwaves at a water/air interface using multiple excitation beams

Marnix Vreugdenhil, Dries van Oosten, and Javier Hernandez-Rueda

Doc ID: 342480 Received 15 Aug 2018; Accepted 08 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: We investigate the formation, propagation and interaction of femtosecond laser induced flows of compressed air at a water/air interface by recording the transient reflectivity of shockwaves. Subsonic fronts of compressed air and weak shockwaves can be hard to detect due to their inherently subtle change of refractive index. Therefore, we study these weak flows by looking at the interaction dynamics of two and four shockwaves simultaneously produced at adjacent locations. An analytic model is used to retrieve the velocity and position of the shockwave from the experimental results. The use of multi-spot excitation opens up a versatile method to further investigate photomechanical tissue damage during fs-laser-based surgery and to study the fluid dynamics of complex systems.

Design and simplified calibration of a Mueller imaging polarimeter for material classification

Yvain QUEAU, Ayman Alfalou, and Florian Leporcq

Doc ID: 344484 Received 30 Aug 2018; Accepted 08 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: This study is concerned with the design of a Mueller imaging polarimeter for the visualization of spatially-varying Mueller matrix fields. A simplified calibration procedure is advocated, where all the optical elements are calibrated simultaneously rather than independently as in the state-of-the-art. This is shown to significantly reduce the bias inherent to sequential calibration methods. In addition, this procedure requires no reference sample, it allows calibration both in transmission or in reflection modes, and it relies on ready-to-use cameras. Put together, these novelties should help non-specialists in optics designing and calibrating a Mueller imaging polarimeter for applications such as material classification.

Interference-Free Hybrid fs/ps Vibrational CARS Thermometry in High-Pressure Flames

Hans Stauffer, Kazi Arafat Rahman, Mikhail Slipchenko, Sukesh Roy, James Gord, and Terrence Meyer

Doc ID: 338575 Received 12 Jul 2018; Accepted 07 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Interference-free hybrid fs/ps vibrational coherent anti-Stokes Raman scattering (CARS) of nitrogen is reported for temperature measurements of 1300– 00 K in high-pressure, laminar H2–air and CH4–air diffusion flames up to 10 bar. Following coherent Raman excitation by 100-fs-duration pump and Stokes pulses, a time-asymmetric probe pulse is used for detection of spectrally resolved N2 CARS signals at probe delays as early as ~200–300 fs. This allows for full rejection of non-resonant contributions while being independent of collisions for single-shot precision of ±2% at elevated pressures. The effects of collisions at longer probe-pulse delays are also investigated to determine the feasibility of varying the detection timing from 200 fs to 100 ps.

Gaussian curvature and stigmatic imaging relations for the design of an unobscured reflective relay

Eric Schiesser, Seung-Whan Bahk, Jake Bromage, and Jannick Rolland

Doc ID: 338523 Received 11 Jul 2018; Accepted 07 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: We derive the relationship between Coddington's equations and the Gaussian curvature for a stigmatic reflective imaging system. This relationship allows parameterizing off-axis conic optical systems using traditional first-order optics by considering the effective curvature at the center of the off-axis sections.Specifically, we demonstrate parameterizing the system requirements of a 2x achromatic image relay for a terawatt laser system. This system required both collimation (far-field) and pupil imaging (near-field) simultaneously. Long working distances and specific spatial constraints limited the available layout options for the imaging components. By parameterizing these system requirements and packaging constraints, the final specifications could be quickly iterated while allowing for flexibility in the layout of the system during a multi-year conceptual period.

Spinning spin density vectors along the propagation direction

Xiaoyan Pang and Wenrui Miao

Doc ID: 339964 Received 17 Jul 2018; Accepted 07 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: It has been known that light possesses both spin and orbital angular momenta (AM) arising from the twisting behaviors of the electric (and magnetic) field vector and the wavefront of the field respectively. The spin (AM) density is also a vector in the field of three dimension (3D), since its orientation can be in any direction. In this letter, we show that through focusing a Gaussian beam with both the on-axis and off-axis vortices in a high numerical aperture system, the spin (AM) density vector in the focal region exhibits nontrivial behaviors: rotating around the central axis along the propagation direction. We demonstrate that this helical behavior of the spin (AM) density vector is mainly caused by the different Gouy phases of the three field components. By changing the position of the off-axis vortex and the semi-aperture angle, the helical shape and the helical length can be adjusted. This new type of optical twists may supply another rotational degree of freedom in opticaltweezers.

Simultaneous Measurement of Millinewton Axial Force and Temperature Using Hybrid Micro-Silica Sphere Fabry-Perot Sensor

Hamid Latifi, omid Ranjbar-Naeini, Mohammad Zibaii, and Ali Mousavian

Doc ID: 341796 Received 08 Aug 2018; Accepted 07 Sep 2018; Posted 20 Sep 2018  View: PDF

Abstract: An optical fiber sensor based on Hybrid Fabry-Perot for simultaneous measurement of millinewton axial forces and temperature is proposed. This structure comprises of a single mode optical fiber (SMF) integrated to a silica capillary tube with Polydimethylsiloxane (PDMS). A Silica Micro Sphere Cavity is fabricated at the tip of capillary tube. Consequently, an air gap followed by a micro-silica sphere forms two cascade cavities. To explain the transferring load from SMF to silica capillary tube through PDMS the shearing mechanism is employed. Experimental result shows that axial force and temperature sensitivities of the air gap cavity in the range of 0-3.43 mN and 30-65 °C are 170pm/mN and 24 pm/°C, respectively, while micro silica sphere cavity did not show any force sensitivity due to its rigidity. However, its temperature sensitivity is 34 pm/°C. The different sensitivities enable us to implement simultaneous sensing of force and temperature.

Characterizations of Reconfigurable IR Metamaterial Absorber with Multi-functional Applications

Ruijia Xu and Yu-Sheng Lin

Doc ID: 336559 Received 03 Jul 2018; Accepted 06 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: We propose four types of metamaterial absorber (MA) to have tunable absorption resonance, polarization-dependent/independent, single-band and dual-band switch characterizations. By tailoring four types of MA with different height between top and bottom metal layers, absorption resonance can be modified 5 μm and absorption intensity can be attenuated gradually. These characteristics of MA devices can be potentially used in variable optical attenuator (VOA). By changing distance between top unit cells of four MA devices, the resonances can be tuned in the range of 1.74 μm with an exponential relationship. All absorption intensities can be maintained over 90%. Furthermore, MA devices also possess single-band and dual-band switch characterizations by controlling polarization angle of incident light, which helps MA to have the potential in multifunctional switch. The switch ratio is calculated to evaluate the performance for dual-band switch. By comparing the range of switch ratios, it can be spanned 1.76 for dual-band switch function. This study provides a strategy to open an avenue for VOA, absorber, detector, sensor, and switch applications in IR wavelength range.

Relaxation of the Crowther criterion in multislice tomography

Chris Jacobsen

Doc ID: 340196 Received 25 Jul 2018; Accepted 06 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: For objects larger than the depth of focus of an imaging system, one must account for wavefield propagation effects within the object as is done in diffraction tomography, diffraction microscopy, and multislice ptychographic tomography. We show here that if the imaging method used reconstructs N_a planes along each viewing direction, one can reduce the number of illumination directions required to fill Fourier space by a factor of 1/N_a, relaxing the usual Crowther criterion for tomography. This provides a conceptual basis to explain two recent experiments where multiple axial planes were imaged per viewing direction, and tomographic images were obtained with good 3D spatial resolution even though fewer illumination directions were used than one would have expected from the Crowther criterion.

Waveguide-Enhanced Raman Spectroscopy of Trace Chemical Warfare Agent Simulants

Nathan Tyndall, Todd Stievater, Dmitry Kozak, Kee Pun Koo, R McGill, Marcel Pruessner, William Rabinovich, and Scott Holmstrom

Doc ID: 342350 Received 16 Aug 2018; Accepted 06 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: Weak scattering cross-sections and low molecular densities have made the development of Raman spectroscopy for trace concentrations of vapor-phase chemical species a challenge. Here, we report the measurement of waveguide-enhanced Raman spectra (WERS) from trace concentrations of four vapor-phase chemical warfare agent simulants: dimethyl methylphosphonate (DMMP), diethyl methylphosphonate (DEMP), trimethyl phosphate (TMP), and triethyl phosphate (TEP). The spectra, which exhibit detection at concentrations as low as 70 parts-per-billion (ppb) and extrapolated one-σ detection limits as low as 5 ppb, are obtained using highly-evanescent nanophotonic silicon nitride waveguides coated with a hyperbranched carbosilane sorbent polymer. We use a finite-element model to explain the polarization and wavelength properties of the differential spectra. In addition, we assign spectral features to both the analyte and the sorbent and show evidence of changes to both due to hydrogen bonding.

Characterisation of a new polymer optical fibre with enhanced sensing capabilities using a Bragg grating

Arnaldo Leal Junior, Antreas Theodosiou, Anselmo Frizera-Neto, Maria Pontes, Ehud Shafir, Oleg Palchik, Nadav Tal, Shlomo Zilberman, Garry Berkovic, Paulo Antunes, Paulo Andre, Kyriacos Kalli, and Carlos Marques

Doc ID: 343022 Received 22 Aug 2018; Accepted 06 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: We present results for the mechanical characterisation of a Bisphenol-A acrylate based polymer optical fibre (POF) manufactured using a novel Light Polymerization Spinning (LPS) process. The particular manufacturing process allows the development of POFs having unique mechanical characteristics, which result from an exceptionally low Young’s modulus. The lower Young’s modulus enables optical sensors for measuring stress or pressure with improved sensitivity and potentially a higher tuneable mechanical range than conventional POFs. Moreover, properties such as the storage modulus variations with respect to the temperature and humidity were studied. Fibre Bragg gratings (FBGs), were inscribed in the POF using the plane-by-plane femtosecond laser, direct-write method for selective FBG mode excitation, and were characterised for changes to temperature, pressure, and relative humidity. The response of FBGs in this LPS-POF, for all the three aforementioned measurands, was several times higher than that measured for conventional POFs.

Switchable dual-wavelength bidirectional Q-switched all-fiber laser using a bidirectional fiber polarizer

zou hang, Qianqian Huang, Tianxing Wang, Zhijun Yan, Mohammed AlAraimi, Alex Rozhin, and Chengbo Mou

Doc ID: 340578 Received 25 Jul 2018; Accepted 05 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: A switchable dual-wavelength bidirectional Q-switched fiber laser using a bidirectional fiber polarizer is demonstrated. 45° tilted fiber grating (45°TFG) is used as a bidirectional fiber polarizer to induce bidirectional intracavity birefringence filter in both clockwise (CW) and counter-clockwise (CCW) directions. Carbon nanotube saturable absorber (CNT-SA) is employed to produce Q-switched pulses. Through adjusting polarization states, switchable single/dual wavelength lasing at 1551 nm, and 1560 nm can be achieved in both CW and CCW directions. To the best of our knowledge, this is the first demonstration of wavelength switchable bidirectional passively Q-switched fiber laser.

Opto-electronic oscillator mediated by acoustic wave in photonic crystal fiber stimulated in 1 µm band

Sigang Yang, Yi yang, Jinyan Li, Siming Ding, Hongwei Chen, Minghua Chen, and Shizhong Xie

Doc ID: 342162 Received 14 Aug 2018; Accepted 05 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: An opto-electronic oscillator based on guided acoustic wave Brillouin scattering in photonic crystal fiber (PCF) stimulated by 1 µm band light wave is proposed and demonstrated. A short length of homemade PCF stimulated by relative low pump power leads to strong coupling between the pump and probe wave. The oscillation is realized in a feedback loop in which the acoustic wave bridges the pump and probe. Oscillation is achieved at 1. 7 GHz, which matches the resonance of the acoustic mode, in a single longitudinal mode operation of the hybrid cavity. It has a high side mode suppression ratio of over 60 dB.

Fluorescence quantum yield and excited state life time determination by phase sensitive photoacoustics: Concept and theory

Thomas Berer and Gregor Langer

Doc ID: 338374 Received 11 Jul 2018; Accepted 05 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: In this letter, we theoretically describe photoacoustic signal generation of molecules, for which triplet re-laxation can be neglected, by considering the excited state lifetime, the fluorescence quantum yield, and the fast vibrational relaxation. We show that the phase response of the photoacoustic signal can be ex-ploited to determine the excited state lifetime of dark molecules. For fluorescent molecules, the phase re-sponse can be used to determine the fluorescence quantum yield directly, without the need of reference samples.

Tunable self-injection locked green laser diode

Md. Hosne Mobarok Shamim, Tien Khee Ng, Boon Ooi, and Mohammed Zahed Khan

Doc ID: 341964 Received 09 Aug 2018; Accepted 05 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: We report the first employment of self-injection locking scheme for the demonstration of a tunable InGaN/GaN semiconductor laser diode. We have achieved 7.11 nm (521.10– 528.21 nm) tunability in green color with different injection currents and temperatures. The system exhibited mode spectral linewidth as narrow as ~69 pm and side mode suppression ratio as high as ~28 dB, with a maximum optical power of ~16.7 mW. In the entire tuning window, extending beyond 520 nm, a spectral linewidth of ≤ 100 pm, high power, and stable performance were consistently achieved, making this first-of-its-kind compact tunable system attractive for spectroscopy, imaging, sensing systems and visible light communication.

On-demand Optomechanical Frequency Comb Memory

Xiaodong Jiang, Arindam Nandi, Dongmin Pak, and Mahdi Hosseini

Doc ID: 340567 Received 27 Jul 2018; Accepted 05 Sep 2018; Posted 12 Sep 2018  View: PDF

Abstract: Typical nano-mechanical oscillator arrays exhibit a mechanical frequency distribution arisen from the imprecision in the nanofabrication process, thus hindering their collective dynamics. We tailor the inhomogeneously broadened spectrum of a nano-oscillator ensemble to unravel the collective dynamics of mechanical oscillators in an optomechanical array. We show that by engineering tunable optomechanical interactions, the instantaneous phase matching between the oscillators reveals collective dynamics in a form of a photon-phonon echo excitation without the need for active frequency tuning. Using numerical simulation, we demonstrate that by controlling such collective dynamics on-demand, broadband and scalable coherent light storage can be realized.

BOMA and OFDM/OQAM modulation for radio over fiber system with enhanced spectral efficiency

Xiaoman Chen, Chang Liu, Laixia Nian, Mengfan Cheng, Songnian Fu, Ming Tang, Deming Liu, and Lei Deng

Doc ID: 336068 Received 26 Jun 2018; Accepted 04 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: A novel radio over fiber system with enhanced spectral efficiency is proposed by using building block sparse constellation-based orthogonal multiple access (BOMA) technique, and orthogonal frequency division multiplexing with offset quadrature amplitude modulation (OFDM/OQAM) technique. With the help of BOMA, the user with good signal-to-noise ratio (SNR) can use the frequency band of the user with poor SNR to transmit extra information by sharing the same well-designed constellation. Moreover, the cycle prefix in OFDM is no longer required due to the properly designed prototype filters in OFDM/OQAM, contributing to the maximum spectral efficiency (SE). To optimize the transmission performance, four types of sparse constellations with different Euclidean distance between constellation points are designed and investigated. In our experiment, the BOMA-OFDM/OQAM signals with the total net rate of 1.84 Gb/s and average SE of 4.6 bit/s/Hz are successfully transmitted over 25.2 km standard single mode fiber for two users with wireless distance of 0.8 m and 0.3 m respectively. The experimental results show that the SE is increased by 37.7% compared with the traditional orthogonal frequency-division multiple access (OFDMA) technique.

Ionic conductivity and its effect on optical properties of LBO crystals

Dmitriy Nikitin, Oleg Ryabushkin, Aleksey Pigarev, and Aleksey Konyashkin

Doc ID: 334652 Received 12 Jun 2018; Accepted 04 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: Temperature dependence of the dielectric losses conditioned by the ionic conductivity of nonlinear optical LBO crystals was investigated both theoretically and experimentally exploiting the variation of the line form of LBO piezoelectric resonances with temperature. An effect of the ionic conductivity on the optical properties of LBO crystals was considered. The relation between the LBO ionic conductivity and its resistance to UV radiation was investigated.

Unusual thermal response of tellurium near-infrared luminescence in phosphate laser glass

Linling Tan, John Mauro, Shanhui Xu, Zhongmin Yang, and Mingying Peng

Doc ID: 340437 Received 24 Jul 2018; Accepted 04 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: We report an unusual thermal response of tellurium near-infrared (NIR) luminescence in phosphate laser glass, where the luminescence first increases and then decreases with heat treatment temperatures increasing from 250 ℃ to the glass transition tem-perature (Tg). This is followed by a distinct revival of Te NIR luminescence at temperatures above Tg. This result differs from the scenario in conventional rare-earth (Er3+, Nd3+ and Yb3+) doped phosphate glasses, where the rare-earth NIR emission decreases with increasing heat treatment temperature. The differ-ence may originate from conversion between Te4 and other tellurium species, which depends on evolution of the glass structure and molecular motion during reheating processes, leading to unusual thermal re-sponse of tellurium NIR luminescence. The increase in Te4 clusters enhances Te NIR emission, indicating that tellurium NIR luminescence is assigned to the Te4 cluster, in contrast to previous studies. Heating and cooling cycles between 50 and 250°C reveal strong dependence of the thermal degradation on glass structure. Tellurium doped phosphate laser glass with zero thermal degradation can be realized by sta-bilizing NIR luminescence center Te4 by adjusting the glass structure with reduced network crosslinking. The superior optical performance has been confirmed in our previous study that the NIR luminescence properties can be well maintained in Te-doped fiber. The findings indicate that tellurium-doped phosphate glass with unusual thermal responses can potentially be used in fiber laser devices.

Pulse characterization by cross-phase modulation in chalcogenide glass

Nurmemet Abdukerim, Imtiaz Alamgir, and Martin Rochette

Doc ID: 340565 Received 25 Jul 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: We report the first all-fiber frequency-resolved optical gating (FROG) device based on cross-phase modulation in chalcogenide glass. The amplitude and phase of pulses as short as 390 fs at femtojoule energy levels are accurately characterized without direction-of-time ambiguity in the retrieved pulse. A measurement sensitivity of 18 mW² is achieved from the strong nonlinearity of a 10 cm long chalcogenide microwire.

Coherence and speckle contrast at the output of a stationary multimode optical fiber

Anatoly Efimov

Doc ID: 343137 Received 24 Aug 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: We relate classic coherence properties of light at the output of a multimode optical fiber excited by a spatially coherent broadband source to speckle contrast measured by two different methods. Speckle contrast measured with an external diffuser is related to the effective number of modes, while that measured over the ensemble of random bends and twists of the fiber is related to the residual coherence defined as a spatial average of the modulus of the classic complex degree of coherence between pairs of widely separated points at the fiber output.

Two-cavity light-trapping scheme used in ultrathin c-Si solar cells

lu Xiaodong, Xinxin Wang, Jie Gao, Yukuo Li, Yang Wang, and Yufeng Zhang

Doc ID: 341821 Received 08 Aug 2018; Accepted 03 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: A new high efficiency light trapping structure (HE-LTS) with two cavities is proposed and designed for ultrathin c-Si solar cells. The results show that by optimizing the size parameters of the HE-LTS, the light absorptance values of a c-Si soar cell with its active layer equal to 4μm are close to that of Lambertian LTS in the wavelength range from 300nm to 900nm and greatly exceed that of Lambertian LTS in the wavelength range from 900nm to 1200nm; the photocurrent density of the HE-LTS can exceed that of Lambertian LTS by adjusting the size parameters in a wide range.

compact broadband silicon 3-dB coupler based on shortcuts to adiabaticity

Tao Chu and guo defen

Doc ID: 338510 Received 13 Jul 2018; Accepted 03 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: We proposed and experimentally demonstrated a compact, broadband, and low-loss mode-evolution based 2 × 2 3-dB coupler on a silicon-on-insulator platform. The waveguide widths and separations of the coupler were tapered in an optimal manner using the shortcuts to adiabaticity method. The coupler, with ∼70-μm total length and 200-nm feature size, exhibited <0.3-dB measured excess loss over a broadband wavelength range from 1500 to 1600 nm. Balanced and unbalanced Mach–Zehnder interferometers fabricated for validation showed extinction ratios larger than 27 dB and dB, respectively, over a 100 nm bandwidth. The extracted splitting ratio was between 0.48 and 0.52.

Dual-focus stimulated Raman scattering microscopy: aconcept for multi-focus scaling

Sandro Heuke, Barbara Sarri, Alberto Lombardini, Xavier Audier, and Herve Rigneault

Doc ID: 335851 Received 22 Jun 2018; Accepted 03 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: High speed imaging is of utmost importance for video-rate live cell investigations or to study extended sample areas at sufficient spatial resolution within reasonable time scales. Improving the speed of single-focus stimulated Raman scattering (SRS) microscopy is ultimately restricted by the sample’s damage threshold and the shot noise of the demodulated laser source. To overcome this limitation we present a dual-focus SRS approach modulating the pump laser for each focus at a distinct frequency. The corresponding probe beams are detected each by a photo diode and demodulated individually by two separate lock-in units to avoid inter-focal cross-talk. Two laterally or axially displaced images as well as hyperspectral SRS images can be obtained simultaneously within the field of view of the objective lens. The modular implementation presented here can be extended to multiple foci by using multi-channel acousto-optics modulators in combination with multi-channel lock-in amplifiers.

Real-time 2-step phase shifting interferometry with full-band interferometric signal recovered

wang yi, Bingbo Li, Qi Cao, Xiaoxu Lu, and Liyun Zhong

Doc ID: 335730 Received 20 Jun 2018; Accepted 03 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: 2-step phase shifting interferometry (PSI) is an important technology for phase retrieval due to its outstanding performance in balancing detector bandwidth, temporal resolution and quantitative quality. The most significant difficulty in this technology should ascribe to the distortion of low spatial frequencies in the retrieved interference signals, which is caused by the imperfect background intensity estimation. This disadvantage has deteriorated its quantitative accuracy to about an order lesser compared with the traditional PSI using 3 or more phase shifting interferograms, especially when the fringe density is not very large. In this latter, we overcome this key difficulty by iteratively recovering the lost spectrum of interferometric signals during spatial filtering and realize truly full space-bandwidth utilization in 2-step PSI. We although use this method to reduce the necessary number of spatially matched cameras in the quadrature real-time phase shifting interferometer to significantly simplify its optical setup.

All-fiber orbital angular momentum mode multiplexer based on mode selective photonic lantern and mode-polarization controller

Xinglin Zeng, Yan Li, Lipeng Feng, Sihan Wu, CHEN YANG, Wei Li, Tong Weijun, and Jian Wu

Doc ID: 341153 Received 31 Jul 2018; Accepted 02 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: We demonstrate, for the first time to the best of our knowledge, an all-fiber orbital angular momentum multiplexer that multiplexes both OAM modes of -l and +l up to second-order by using a mode selective photonic lantern and a mode-polarization controller. The experimentally obtained mode profiles are close to the theoretical results and the mode purities are higher than 89% for all the OAM modes at 1550 nm. The losses for all modes generations are less than 3.8dB in the C band.

Chaotic time-delay signature suppression with bandwidth broadening by fiber propagation

Song-Sui Li, Xiao-zhou Li, and Sze-Chun Chan

Doc ID: 338824 Received 17 Jul 2018; Accepted 01 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: Chaotic emission of a semiconductor laser is investigated through propagation over a fiber for achieving broadening of the bandwidth and suppression of the time-delay signature (TDS). Subject to delayed optical feedback, the laser first generates chaos with a limited bandwidth and an undesirable TDS. The laser emission is then delivered over a standard single-mode fiber for experiencing self-phase modulation together with anomalous group-velocity dispersion, which lead to broadening of the optical bandwidth and suppression of the TDS in the intensity signal. The effects are enhanced as the input power launched to the fiber increases. By experimentally launching up to 340 mW into a 20-km fiber, the TDS is suppressed by 10 times to below 0.04, while the bandwidth is broadened by 6 times to above 100 GHz. The improvement of the chaotic signal is potentially useful in random bit generation and range detection applications.

Theory of thermo-optic instabilities in dual-core fiber amplifiers

Jesper Laegsgaard, Federica Poli, Annamaria Cucinotta, and Stefano Selleri

Doc ID: 341143 Received 31 Jul 2018; Accepted 01 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: A coupled-mode theory for nonlinear mode coupling by the thermo-optic effect, originally developed for single-core fiber amplifiers is applied to the case of dual-core amplifiers. It is shown that a non-phase-matched coupling term, which is usually irrelevant in single-core amplifiers, can strongly affect mode stability when the coupling length between supermodes exceeds a few centimeters. The phase-mismatched coupling can lead to a strongly reduced instability threshold and static deformation effects for a range of intermediate coupling lengths.

8-channel laser array with 100 GHz channel spacing based on surface slotted structures fabricated by standard lithography

Mingjin Wang, Hailing WANG, Pijie Ma, Fengxin Dong, Anjin Liu, and Wan-hua Zheng

Doc ID: 338754 Received 18 Jul 2018; Accepted 01 Sep 2018; Posted 06 Sep 2018  View: PDF

Abstract: An 8-channel laser array with 100 GHz channel spacing based on surface slotted structures is demonstrated. Wavelength selection is realized by using a group of micrometer-order slots fabricated by standard lithography technology. The output power of over 14mW and SMSR of better than 35 dB for each laser within the array are achieved. The laser array without tuning for 100 GHz channel spacing by standard lithography was realized for the first time, to the best of our knowledge. The laser array can be used to enhance the capacity of communication links and provides a promising light source for photonic integrated circuit.

High-resolution deep two-photon imaging with large back aperture objectives using intracavity modulation and extended-line temporal focusing

Kai Lou, Bo Wang, Ah-Young Jee, Steve Granick, and Francois Amblard

Doc ID: 341776 Received 08 Aug 2018; Accepted 01 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: With the introduction of an intracavity modulation of the femtosecond laser spectrum to adaptively fill the back aperture of the objective lens, line-temporal focusing two-photon microscopy is demonstrated to reach near-diffraction-limited axial resolution with a large back aperture objective lens, and improved immunity to sample scattering. In addition, a new flattop beam shaping method is proposed which provides a uniform contrast with little degradation of the axial resolution along the focus line and in the depth. This is demonstrated in fast, large volumetric imaging of mouse lung samples.

Wide-angle giant transverse magneto-optical Kerr effect in a gyromagnetic superlens

Mehdi Zamani and Mansoureh Amanollahi

Doc ID: 331681 Received 15 May 2018; Accepted 01 Sep 2018; Posted 11 Sep 2018  View: PDF

Abstract: In this letter, we report a gyromagnetic superlens having giant transverse magneto-optical Kerr effect (TMOKE) in a wide-range of incident angles. The existence of loss is the heart of existence of TMOKE, and we found that the wide-angle giant TMOKE is occurred when this loss is due to permittivity, while the gyration parameter is due to permeability. Herein, the permeability of the mentioned gyromagnetic slab is tensor and only responds to s-polarized (TE) light.

Strong coupling between magnetic plasmons and surface plasmons in a black phosphorus-spacer-metallic grating hybrid system

Yeming Qing, Hui Feng Ma, and Tie Jun Cui

Doc ID: 342394 Received 14 Aug 2018; Accepted 01 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: We propose a black phosphorus-spacer-metallic grating hybrid system to investigate the strong coupling between black phosphorus surface plasmons (BPSP) and magnetic plasmons (MP) at far-infrared frequencies. We illustrate theoretically and numerically interactions between the BPSP mode and MP mode in the coupling regime, which leads to a prominent Rabi splitting and the formation of multiple hybrid modes. Since the mechanisms of the two resonance modes are completely different, the fields in the system can be selectively localized in the spacer layer or metallic slits by regulating the coupling between such modes. Due to the strong anisotropic in-plane properties of BP, the coupling between BPSP and MP modes in both armchair and zigzag directions is quite different. This work offers a new paradigm to enhance the light-matter interaction through the coupling of multiple resonance modes, and the proposed device will provide potential applications in constructing easy-to-fabricate BP-based plasmonic devices.

Deeply seeing through highly turbid water by active polarization imaging

Fei Liu, Pingli Han, Yi Wei, kui yang, Shengzhi Huang, xuan Li, Lu Bai, Xiaopeng Shao, and Guang Zhang

Doc ID: 339968 Received 31 Jul 2018; Accepted 31 Aug 2018; Posted 06 Sep 2018  View: PDF

Abstract: We hereby proposed and experimentally demonstrated an active polarization imaging technique, based on wavelength selection, for seeing through highly turbid water where targets are always visually lost. The method was realized by making use of the dependence of light scattering on wavelength in turbid water. Red light illumination was selected to minimize scattering occurred in light propagation and to guarantee accurate estimation of Degree of Polarization (DoP). Experiments demonstrate its contribution to make targets in highly turbid water from “undetectable” to “detectable”.

Transmission Matrix-based Electric field Monte Carlo Study and Experimental Validation of the Propagation Characteristics of Bessel Beams in Turbid Media

Xiuwei Zhu, Luyao Lu, Zi Cao, Bixin Zeng, and Min Xu

Doc ID: 336390 Received 04 Jul 2018; Accepted 31 Aug 2018; Posted 07 Sep 2018  View: PDF

Abstract: A novel Transmission matrix-based Electric field Monte Carlo (TEMC) method is introduced to study the propagation characteristics of Bessel beams with different orbital angular momentum (OAM) in turbid media. As an extension to the Electric field Monte Carlo (EMC) approach, electric field transmission modes were simulated to properly evaluate light interference. Beam transmission patterns, intensity attenuation and the degree of polarization (DOP) through turbid media of varying thickness were analyzed. It was found that the OAM plays a subtle role in transmission through turbid media, showing only a weak correlation with total transmission, the preservation of DOP, and the penetration depth. The TEMC simulation results were in excellent agreement with experiments, validating the proposed method for the study of coherence phenomenon in turbid media.

Depth of field extended scattering imaging by light field estimation

Xin Jin, Zhouping Wang, Xiaoyu Wang, and Qionghai Dai

Doc ID: 341372 Received 02 Aug 2018; Accepted 31 Aug 2018; Posted 07 Sep 2018  View: PDF

Abstract: Imaging through scattering media is challenging especially for 3D scenarios. A lot of efforts have been made, while they suffer from tedious point spread function (PSF) acquisition process or limited depth of field (DOF). In this letter, a DOF extended scattering imaging method is proposed based on light field estimation. Using speckle intensities captured at two depths as constraints, fast wavefront recovery model is proposed to estimate the phases with low computational complexity. Secondary propagation of recovered wavefront is performed to generate the speckle intensity patterns at the target depths and they are utilized to deconvolute integrated intensity matrices (IIMs) for extending imaging DOF. The effectiveness of the proposed method is demonstrated by both simulated and real experiments. © 2018 Optical Society of America

Dual-view photoacoustic microscopy for quantitative cell nuclear imaging

De Cai, Terence T. W. Wong, Liren Zhu, Junhui Shi, Sung-Liang Chen, and Lihong Wang

Doc ID: 340705 Received 25 Jul 2018; Accepted 31 Aug 2018; Posted 10 Sep 2018  View: PDF

Abstract: Optical-resolution photoacoustic microscopy (OR-PAM) is an emerging imaging modality for studying biological tissues. However, in conventional single-view OR-PAM, the lateral and axial resolutions—determined optically and acoustically, respectively—are highly anisotropic. In this Letter, we introduce dual-view OR-PAM (DV-OR-PAM) to improve the axial resolution, achieving three-dimensional (3D) resolution isotropy. We first use 0.5 μm polystyrene beads and carbon fibers to validate the resolution isotropy improvement. Imaging of mouse brain slices further demonstrates the improved resolution isotropy, revealing the 3D structure of cell nuclei in detail, which facilitates quantitative cell nuclear analysis.

High-sensitivity vector magnetic field sensor based on side-polished fiber plasmon and ferrofluid

Zhupeng Jiang, Jiangli Dong, Shiqi Hu, Yaxin Zhang, Yaofei Chen, Yunhan Luo, Wenguo Zhu, Wentao Qiu, Huihui Lu, Heyuan Guan, Yongchun Zhong, Jianhui Yu, Jun Zhang, and Zhe Chen

Doc ID: 341297 Received 02 Aug 2018; Accepted 31 Aug 2018; Posted 04 Sep 2018  View: PDF

Abstract: A high-sensitivity vector magnetic field sensor based on side-polished fiber and ferrofluid is proposed and demonstrated. The sensor consists of a fiber-based surface plasmon resonance (SPR) structure, which is realized by depositing a gold film onto a side-polished multimode fiber, and the surrounding ferrofluid. Because of the high refractive index sensitivity of SPR scheme and the outstanding magneto optical properties of ferrofluid, the sensor has a high sensitivity (up to 598.7 pm/Oe) to the magnetic field intensity. Moreover, owing to the non-circular-symmetric geometry of the side-polished fiber and the non-uniform distribution of ferrofluid around fiber, the sensor can also exhibit a sensitivity of -5.63 nm/deg to the orientation of magnetic field. The proposed vector magnetic field sensor, integrating over magnetic, plasmonic and fiber-optic scheme, and simultaneously showing high sensitivity to magnetic intensity and orientation, is meaningful and will have potential applications in many fields, such as modern industry, national defense and military.

Strong Light Confinement in Rod-Connected Diamond Photonic Crystals

Ying-Lung Ho, Mike Taverne, Xu Zheng, Lifeng Chen, Chen-Hsuan Fang, and John Rarity

Doc ID: 340948 Received 14 Aug 2018; Accepted 31 Aug 2018; Posted 04 Sep 2018  View: PDF

Abstract: We show that it is possible to confine light in a volume of order 10-³ cubic wavelengths using only dielectric material. Low-index (air) cavities are simulated in high index rod-connected diamond (RCD) photonic crystals. These cavities show long storage times (Q-factors >10⁶) even at the lowest volumes. Fabrication of such structures could open up a new field of photon level interactions.

Role of refractive index mismatch on SHG imaging and the forward-to-backward ratio

Jarno van der Kolk, Stephane Bancelin, Charalambos Kioulos, Antonino Cala' Lesina, François Légaré, and Lora Ramunno

Doc ID: 341639 Received 13 Aug 2018; Accepted 31 Aug 2018; Posted 12 Sep 2018  View: PDF

Abstract: Nonlinear optical imaging in the epi-direction is used to image subresolution features. We find that a refractive index mismatch between the object to be imaged and the background medium can change the far-field intensity image. As an example, we study second harmonic generation microscopy where the forward-to-backward ratio is used to quantify subresolution features. We show both theoretically and experimentally that the inhomogeneous refractive index in collagen tendon tissue creates near-field effects which can change the F/B ratio by \char`~20--\SI[detect-all = true]{25}{\percent}, even though the effect is negligible for most of the individual fibrils in the tissue. This is caused by the sensitivity of the backward signal on phase-matching conditions.

Dielectric Properties of Conductively LoadedPolyimides in the Far Infrared

Kyle Helson, Edward Wollack, Karwan Rostem, Kevin Miller, and Manuel Quijada

Doc ID: 337884 Received 05 Jul 2018; Accepted 30 Aug 2018; Posted 30 Aug 2018  View: PDF

Abstract: The dielectric properties of selected conductively loadedpolyimide samples are characterized in microwavethrough far infrared wavebands. These materials,belonging to the Vespel® family, are more readilyformed by direct machining than their ceramicloaded epoxy counterparts and present an interestingsolution for realizing absorptive optical control structures.Measurements spanning a spectral range from 1to 600 cm¯¹ (0.03 to 18 THz) were preformed and usedin parametrization of the media’s dielectric function atfrequencies below ~3 THz.

Intensity mediated change in sign of ultrafast third-order nonlinear optical response in As2S2 thin films

Dipendranath Mandal, RAJESH YADAV, Anirban Mondal, SANTU BERA, JR Aswin, Petr Nemec, Tomas Halencovic, and KV Adarsh

Doc ID: 336488 Received 03 Jul 2018; Accepted 30 Aug 2018; Posted 04 Sep 2018  View: PDF

Abstract: We study experimentally and theoretically the intensity-dependent off-resonant ultrafast third-order nonlinear optical response of As2S2 thin films. At low intensity, we observed saturable absorption with negative (self-defocusing) nonlinear refractive index (n2) which at higher intensity switched over to reverse saturable absorption with a change in sign of n2 to positive (self-focusing). Our findings constitute the compelling evidence on how to dynamically tune the optical response with the intensity that has its origin on the combined effect of two photon absorption and Pauli blocking. The results were explained with the help of time-resolved measurements, and rigorous theoretical and numerical simulations.

Disordered spontaneously buckled optical gratings for improved lighting applications

Bruce Bernacki, Kyle Alvine, and Brent DeVetter

Doc ID: 336175 Received 28 Jun 2018; Accepted 30 Aug 2018; Posted 06 Sep 2018  View: PDF

Abstract: Technologies for directing daylight deeper within a building space are highly sought after for energy efficiency applications in order to offset artificial lighting costs and to improve workplace productivity via the use of natural light. Vertical window coatings that can perform this task by redistributing sunlight deeper into a space are especially attractive as they are significantly more straightforward to incorporate into a wide variety of architectures as well as to retrofit into existing facades as compared to roof-based skylights or bulky horizontal daylight shelf type options. The potential energy savings are even greater when one takes into account the fact that such technologies would mitigate harsh glare, allowing window shades to be open for longer portions of the day. However, low-cost and readily scalable techniques are essential for widespread adoption of these window coating technologies. Here, we describe a potentially low-cost method to create a window coating that could enhance daylight penetration, requiring only a thin film of polymeric material deposited on an elastomeric substrate. The resulting structure is a disordered, spontaneously buckled optical grating that spreads incident light without noticeable chromatic dispersion due to its stochastic patterning. The described method has the potential to improve energy efficiency and while maintaining acceptable optical clarity.

1.2 kW clad pumped Raman all-passive-fiber-laser with brightness enhancement

Yaakov Glick, Yariv Shamir, Matitya Aviel, Yoav Sintov, Sharone Goldring, noam shafir, and Shaul Pearl

Doc ID: 336047 Received 10 Jul 2018; Accepted 29 Aug 2018; Posted 30 Aug 2018  View: PDF

Abstract: An all-fiber clad pumped Raman fiber laser oscillator with a CW power of 1.2 kW and an efficiency of 85% is presented. To the best of our knowledge, this laser is the highest power and the highest efficiency Raman fiber laser demonstrated in any configuration with brightness enhancement. It is also the first >kW fiber laser of any kind, not utilizing rare earth doping in the oscillator fiber. The beam quality of the Raman laser was M2=2.75 at 1 kW and the pump-Stokes brightness enhancement factor was approximately 7. The laser consists of a specially designed triple-clad fiber which confines the low beam quality pump power into the multi-mode inner clad while generating the Raman signal in the LMA core. The second Stokes is inhibited by selecting the appropriate inner clad to core area ratio and by the oscillator's selective fiber Bragg grating reflectors.

Verification of transverse translation diverse phase retrieval for concave optical metrology

Aaron Michalko and James Fienup

Doc ID: 340866 Received 27 Jul 2018; Accepted 29 Aug 2018; Posted 05 Sep 2018  View: PDF

Abstract: The surface figure error of a concave spherical mirror was measured using transverse translation diverse phase retrieval (TTDPR), an image-based wavefront sensing technique. Good reproducibility of the surface measurement is demonstrated. Additionally, the TTDPR measurement of the surface, with certain alignment terms removed, is shown to agree to interferometric measurements to 0.0060 waves RMS.

Pump wavelength dependence and thermal effect of photobleaching of BAC-Al in bismuth/erbium codoped aluminosilicate fibers

Zhao Qiancheng, Yanhua Luo, Yuan Tian, and Gang-Ding Peng

Doc ID: 343135 Received 24 Aug 2018; Accepted 28 Aug 2018; Posted 04 Sep 2018  View: PDF

Abstract: Photobleaching of IR luminescence of BAC-Al at 1180 nm under various irradiation wavelengths (532, 633, 710, 830, 980 nm) is observed for the first time. It’s found that the bleaching rate increases along with the increasing photon energy. The photobleaching of BAC-Al at 532 nm irradiation is described as a two-photon process, evidenced by the quadratic dependence of the bleaching rate on the launched power. The photoinduced reduction on absorption bands of BAC-Al (700 nm) and BAC-Si (816 nm) is observed, revealing the higher stability for BAC-Al to laser irradiation. The thermal annealing effect on the bleached BAC-Al is also investigated, strong luminescence quenching of BAC-Al at high temperature (500°C) is shown instead of the recovery. The underlying mechanism for photobleaching and thermal quenching of BAC-Al is analyzed and discussed.

High-contrast infrared polymer photonic crystals fabricated by direct laser writing

Yanzeng Li, Daniel Fullager, Serang Park, Darrell Childers, Ronnie Fesperman, Glenn Boreman, and Tino Hofmann

Doc ID: 340296 Received 27 Jul 2018; Accepted 28 Aug 2018; Posted 29 Aug 2018  View: PDF

Abstract: One-dimensional photonic crystals were fabricated by three-dimensional direct laser writing using a single polymer to obtain reflectance values approaching that of a gold reference in the near-infrared spectral range. The photonic crystals are composed of alternating compact and low-density polymer layers which provide the necessary periodic variation of the refractive index. The low-density polymer layers are composed of subwavelength-sized pillars which simultaneously serve as a scaffold while also providing refractive index contrast to the adjacent compact polymer layers. Bruggemann effective medium theory and stratified-layer optical-model calculated reflectivity profiles were employed to optimize the photonic crystal's design to operate at a desired wavelength of 1.55 μm. After the fabrication, the photonic crystal's structure was compared to the nominal geometry using complementary scanning electron microscopy and optical microscopy micrographs identifying a true-to-form fabrication. The performance of the photonic crystals was investigated experimentally using FTIR reflection and transmission measurements. A good agreement between stratified-layer optical-model calculated and measured data is observed. We thereby demonstrate the ease of predictive design and fabrication of highly efficient one-dimensional photonic crystals for the infrared spectral range using three-dimensional direct laser writing of a single polymer.

Ultrafast physical random bit generation from a chaotic oscillator with silicon modulator

Lei Zhang, Wenjing Tian, jianfeng ding, Sizhu Shao, Xin Fu, and Lin Yang

Doc ID: 335389 Received 18 Jun 2018; Accepted 28 Aug 2018; Posted 28 Aug 2018  View: PDF

Abstract: We demonstrate physical random bit (PRB) generation from two chaotic optoelectronic oscillators (OEOs) with silicon Mach-Zehnder (MZ) and microring resonator (MRR) modulators, respectively. The carrier-injection modulation and the beam interference provide the nonlinearity for the OEO. We digitalize the analog chaotic signals from the two OEOs at 40 GS/s with 8-bit resolution and use self-delay bitwise XOR operation as the post-processing method. The randomness of the resulting 320-Gbps PRB sequences is verified by the NIST SP800-22 statistical tests. With the progress of silicon photonic circuits, there is a potential to fabricate a monolithic chaotic OEO chip for compact PRB generation.

Proof of principle implementation of phase-flip error rejection quantum key distribution

Juan Wu, Xue-bi An, Zhen-Qiang Yin, Fang-Xiang Wang, Wei Chen, Shuang Wang, Guang-can Guo, and Zhengfu Han

Doc ID: 341466 Received 02 Aug 2018; Accepted 28 Aug 2018; Posted 28 Aug 2018  View: PDF

Abstract: Improving the tolerance of channel noise is an important task for devising and implementing quantum key distribution (QKD) protocol. Quantum phase-flip error rejection(QPFER) code [Physical Review Letters 92, 077902 (2004)] has been introduced by X. B. Wang to increase the tolerable phase-flip noise of QKD implementations. However, an experiment that demonstrates its advantages is still missing. Here, we experimentally verify QPFER code with the assistance of two photon quantum states generated by spontaneous parametric down conversion. The methods of parity check and post-selection are introduced to the protocol for achieving the phase-flipping rejection. Comparing with the standard realization of the single photon polarization encoding BB84 scheme, the quantum error rate(QER) after decoding is obviously reduced when the probability of channel noise is less than 25$\%$. Our results show that QPFER protocol can reduce more error rate, obtain a high key rate, and robust in the symmetric and independent random noisy channel.

Multiplexing and tuning of a double set of resonant modes in optical microtube cavities monolithically integrated on a photonic chip

Abbas Madani, Ehsan Saei Ghareh Naz, Stefan Harazim, Moritz Kleinert, YIN YIN, Libo Ma, and Oliver Schmidt

Doc ID: 341417 Received 02 Aug 2018; Accepted 27 Aug 2018; Posted 28 Aug 2018  View: PDF

Abstract: We experimentally demonstrate a monolithic integration of two vertically rolled-up microtube resonators (VRUMs) on polymer-based 1×5 multimode interference (MMI) waveguides to achieve 3D multi-channel coupling. In this configuration, different sets of resonant modes are simultaneously excited at S-, C-, and L- telecom bands, demonstrating an on-chip multiplexing based on vertical coupling configuration. Moreover, the resonant wavelength tuning and consequently the overlapping of resonant modes is accomplished via covering the integrated VRUMs by liquid. A maximum sensitivity of 330 nm/refractive index unit is achieved. The present work would be a critical step for the realization of massively parallel optofluidic sensors with higher sensitivity and flexibility for signal processing, particularly in a three-dimensionally integrated photonic chip.

Super-Resolution Imaging by Anticorrelation of Optical Intensities

Xi-Hao Chen, Shao-Ying Meng, Ying-Hui Sha, Qiang Fu, Qian-Qian Bao, Wei-Wei Shi, Guo-Dong Li, and Ling-An Wu

Doc ID: 338155 Received 09 Jul 2018; Accepted 27 Aug 2018; Posted 27 Aug 2018  View: PDF

Abstract: Photon bunching, a feature of classical thermal fields, has been widely exploited to implement ghost imaging. Here, we show that spatial photon antibunching can be experimentally observed via low-pass filtering of the intensities of the two thermal light beams from a beamsplitter correlation system. Through suitable choice of the filter thresholds, the minimum of the measured normalized anti-correlation function, i.e. antibunching dip, can be lower than 0.2, while its full-width-at-half-maximum can be much narrower than that of the corresponding positive correlation peak. Based on this anti-correlation effect, a super-resolution negative ghost image is achieved in a lensless scheme, in which the spatial resolution can exceed the Rayleigh diffraction limit by more than a factor of two. The setup is quite simple and easy to implement, which is an advantage for practical applications.

Ultrafast miniature fiber-tip Fabry-Perot humidity sensor with thin graphene oxide diaphragm

Cheng Li, Xiyu Yu, Wei Zhou, Yubo Cui, Jian Liu, and Chun Fan

Doc ID: 340468 Received 26 Jul 2018; Accepted 27 Aug 2018; Posted 29 Aug 2018  View: PDF

Abstract: We demonstrate here an ultrafast, miniature and high-performance fiber-tip Fabry-Perot (F-P) humidity sensor with ~300-nm thick graphene oxide (GO) diaphragm suspended onto the endface of a capillary tube with an inner diameter of 50 m and cavity length of ~100 m. The sensitivity to relative humidity (RH) spanning from ~10 %RH to ~90 %RH was examined based on the wavelength shift in interference spectrum. Due to the intrinsic hydrophilicity of porous GO membrane, the developed sensor exhibited an average wavelength variation of ~0.2 nm/%RH, which indicated a relatively broad and readily detectable RH linear measurement range. More prominently, an ultrahigh response time of 60 ms was achieved over other alternative F-P humidity sensors previously reported to our knowledge.

Partially-coherent illumination engineering for enhanced refractive index tomography

Jose Rodrigo, Juan Soto, and Tatiana Alieva

Doc ID: 341302 Received 02 Aug 2018; Accepted 27 Aug 2018; Posted 29 Aug 2018  View: PDF

Abstract: Optical diffraction tomography based on partially coherent illumination (PC-ODT) is a quantitative label-free imaging technique that allows reconstructing the object's 3D refractive index from measured through-focus intensity images. PC illumination provides advantages such as speckle noise-free imaging and inherent compatibility with conventional wide-field microscopes. Here, we experimentally demonstrate that a proper design of the PC illumination, different to the familiar bright-field one, and the use of more realistic optical transfer functions (OTFs) have a crucial importance in PC-ODT to significantly increase the accuracy in 3D RI reconstruction. While realistic OTFs properly account for the real experimental illumination conditions, the proposed PC illumination design allows for gathering the object spatial-frequency content attenuated when bright-field illumination is used.

Simplified Sum Frequency Generation Using a Narrow Free-Spectral-Range Etalon

Isaac Prichett and Aaron Massari

Doc ID: 338800 Received 16 Jul 2018; Accepted 27 Aug 2018; Posted 04 Sep 2018  View: PDF

Abstract: We report the implementation of a narrow free spectral range Fabry-Perot etalon for multiplex vibrational sum frequency generation (VSFG) spectroscopy. Moreover, we demonstrate the use of the etalon reflection to simultaneously generate a broadband infrared pulse, which enables a multiplex VSFG spectrometer using a total of 0.58 W. VSFG spectra with and without the non-resonant background suppressed were simultaneously collected utilizing the time-asymmetry in the upconverting pulse. Two examples are demonstrated in which spectral perturbations can be induced by the time asymmetric pulse even without non-resonant suppression.

Imaging of guided waves using an all-fiber reflection-based apertureless NSOM with self-compensation of phase drift

Yi-Zhi Sun, Binbin Wang, Rafael Salas-Montiel, Sylvain Blaize, Renaud Bachelot, Li Shuang Feng, and Wei Ding

Doc ID: 336514 Received 02 Jul 2018; Accepted 27 Aug 2018; Posted 10 Sep 2018  View: PDF

Abstract: A phase-resolved reflection-based apertureless nearfield scanning optical microscope with an original all-fiber configuration is presented. Our system consists of an intrinsically phase-stable common-path interferometer. The reflection from the waveguide input facet or from an integrated fiber Bragg grating is used as the reference beam. This arrangement effectively suppresses the phase drift caused by environmental fluctuations. By raster scanning a silicon atomic force microscope probe, we measure the complex near fields of the propagating and stationary waves in silicon nanowaveguides. Our robust, align-free, cost effective, and shot-noise limited near-field imaging technique paves the way for versatile optical characterizations of nanophotonic structures on a chip.

Swept-source OCT microsystem with integrated Mirau interferometer and electrothermal micro-scanner

Przemyslaw Struk, Sylwester Bargiel, Quentin Tanguy, Fernando Garcia Ramirez, Nicolas Passilly, Philippe Lutz, olivier gaiffe, Huikai Xie, and Christophe Gorecki

Doc ID: 335148 Received 19 Jun 2018; Accepted 24 Aug 2018; Posted 06 Sep 2018  View: PDF

Abstract: In the rapid evolution of gastrointestinal endomicroscopy, Optical Coherence Tomography (OCT) has found many diverse applications. Until recently, MOEMS (micro-opto–electro-mechanical systems) technology has been playing a key role in shaping the miniaturization of these components. We report here a novel endoscopic microsystem based on a spectrally tuned Mirau micro-interferometer integrated with a MEMS electro-thermal micromirror, operating in the regime of swept- source OCT (SS-OCT) imaging. This article validates our initial proof-of-concept toward development of such MOEMS probe and the presentation of experimental performances of the SS-OCT microsystem.

Broadband multilayer antireflection coating for quantum cascade laser facets

Yohei MATSUOKA, Mykhaylo Semtsiv, Sven Peters, and W. Masselink

Doc ID: 341373 Received 01 Aug 2018; Accepted 24 Aug 2018; Posted 29 Aug 2018  View: PDF

Abstract: We demonstrate a broadband multilayer anti-reflection (AR) coating applied on a quantum cascade laser (QCL) facet. The bandwidth of the AR coating was optimized for the range of 8.0 to 12.0 μm to cover the entire emission spectrum of a broad-gain QCL. The laser facets are high reflectance- and AR-coated for use in an external cavity QCL. The AR coating comprises layers of yttrium fluoride, zinc sulfide, and germanium, all deposited using electron-beam evaporation, and the modal reflectance of the laser facet was reduced to 0.75%. The external cavity laser performance in a Littrow-type configuration is also described.

Phase structuring of the complex degree of coherence

Olga Korotkova and Xi Chen

Doc ID: 341760 Received 07 Aug 2018; Accepted 23 Aug 2018; Posted 29 Aug 2018  View: PDF

Abstract: Simple conditions on the magnitude and phase ofthe complex degree of coherence of stationary, scalar,one-dimensional Schell-like sources are derived fordesign of novel optical beam-like fields. Several examplesof new sources obtained with the help ofsignum, odd monomials and sine phase functions aregiven. A geometrical representation, termed coherencecurve, for the complex coherence state of a one-dimentional,Schell-like source with non-trivial magnitudeand phase distributions by means of a parametriccurve confined to the unit circle in a complex plane isalso introduced.

Efficient directly emitting high power Tb3+:LiLuF4 laser operating at 587.5 nm in the yellow range

Elena Castellano-Hernández, Philip Metz, Maxim Demesh, and Christian Kraenkel

Doc ID: 338203 Received 18 Jul 2018; Accepted 23 Aug 2018; Posted 04 Sep 2018  View: PDF

Abstract: We present the most efficient solid-state laser directly emitting in the yellow spectral range. Without any nonlinear conversion steps, a Tb3+:LiLuF4 laser operates at a wavelength of 587.5 nm with an output power of 0.5 W and a record high slope efficiency of 25 % with respect to the absorbed pump power at 486.2 nm. Despite the detrimental influence of 4f-excited state absorption, this efficiency is comparable to those obtained by complex nonlinear methods to generate yellow laser emission. Our approach, in combination with the progress in laser diodes at the required pump wavelength, paves the way for the development of cost-efficient, robust, and easily manageable diode pumped yellow laser sources.

Plasmonic Metasurfaces for Subtractive Color Filtering: Optimized Non-Linear Regression Models

Walied Sabra, Shaimaa Azzam, Maowen Song, MICHAEL POVOLOTSKYI, Arafa Aly, and Alexander Kildishev

Doc ID: 340374 Received 23 Jul 2018; Accepted 19 Aug 2018; Posted 06 Sep 2018  View: PDF

Abstract: We develop and explore a non-linear regression modeling approach to designing subtractive color filters (SCFs) based on plasmonic metasurfaces. The approach opens up the possibility of rapidly choosing a desired optimized SCF design with high color saturation and brightness using an analytical expression. In our study, colors are produced by absorbing light of specific wavelengths and reflecting the remaining spectrum with silver gap-plasmon nano antennas deposited on a silver film. First, we design three different SCFs – yellow, magenta, and cyan. Then, by adjusting the design parameters of the nanoantennas, we optimize their high absorption resonance peaks (reflections dips), which are tunable over the visible spectrum. Finally, by using non-linear regression analysis, we fit our results to a cubic regression model. Accordingly, a SCF for a color of choice can be designed in a straightforward way. This is a promising technique that provides a methodology to design preoptimized filters for practical applications such as color printing, high-resolution chromatic displays, and multi-spectral imaging.

106 W, picosecond Yb-doped fiber MOPA system with a radially polarized output beam

Di Lin, Shaif-Ul Alam, David Richardson, and Neda Baktash

Doc ID: 340924 Received 31 Jul 2018; Accepted 14 Aug 2018; Posted 15 Aug 2018  View: PDF

Abstract: We report the generation of high average output power, high peak power and high pulse energy radially polarized picosecond pulses from a compact gain-switched laser-diode-seeded Yb-doped fiber (YDF) master oscillator power amplifier (MOPA) system. A q-plate was employed as a mode converter prior to the final power amplifier to efficiently convert the linearly polarized Gaussian-shaped beam into a donut-shaped radially polarized beam. The desired vector beam was efficiently amplified yielding ~110ps pulses with a maximum output pulse energy of ~30.7µJ and a peak power of ~280kW at a repetition rate of 1.367MHz. The average power was scaled up to 106W by increasing the repetition rate to 5.468MHz

Photonics in highly dispersive media: The exact modal expansion

Frederic Zolla, Andre Nicolet, and Guillaume Demesy

Doc ID: 338174 Received 09 Jul 2018; Accepted 28 Jul 2018; Posted 30 Jul 2018  View: PDF

Abstract: We present exact modal expansions for photonic systems including highly dispersive media. The formulas, based on a simple version of the Keldysh theorem, are very general since both permeability and permittivity can be dispersive, anisotropic, and even possibly non reciprocal. A simple dispersive test case where both plasmonic and geometrical resonances strongly interact exemplifies the numerical efficiency of our approach.

Strain sensing based on a microbottle resonator with cleaned-up spectrum

Yiheng Yin, Yanxiong Niu, Mengxin Ren, Wei Wu, weisheng zhao, Jian Nan, Zhenyi Zheng, Yue zhang, and Ming Ding

Doc ID: 330953 Received 07 Jun 2018; Accepted 25 Jul 2018; Posted 29 Aug 2018  View: PDF

Abstract: In this paper, a strain sensor based on the microbottle resonator with individual mode distribution and recognizable resonance spectrum was proposed and demonstrated. The cleaned-up spectrum was achieved by inscribing horizontal microgroove scars rather close to the bottle center. The inscribing parameters of the grooves were designed according to the axial field distribution of the modes, and the obtained spectrum showed excellent consistent with the theoretical analyzation. The shift of the resonance peak as the increase of stretching force was investigated, and the corresponding strain sensitivities were 0.085 pm/με for TE polarization and 0.136 pm/με for TM polarization, which could be further increased by using materials with smaller elastic modulus.

Non-destructive characterization of rare-earth-doped optical fiber preforms

Marilena Vivona, Jae Sun Kim, and Michalis Zervas

Doc ID: 334155 Received 05 Jun 2018; Accepted 26 Jun 2018; Posted 27 Jun 2018  View: PDF

Abstract: We present a non-destructive optical technique for rare-earth-doped optical fiber preform inspection, which combines luminescence spectroscopy measurements, analyzed through an optical tomography technique, and ray-deflection measurements for calculating the refractive index profile of the sample. We demonstrate the technique on an optical fiber preform sample with an Yb3+-doped aluminosilicate core. The spatial distribution of the photoluminescence signals originating from Yb3+-single ions and from Yb3+-Yb3+ cluster sites were obtained inside the core. By modifying the characterization system, we were able to concurrently evaluate the refractive index profile of the core, and thus establishing with good accuracy the dopant distribution within the core region. This technique will be useful for quality evaluation and optimization of optical fiber preforms.

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