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Accepted papers to appear in an upcoming issue

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Highly efficient optical parametric amplifier tunablefrom near-IR to mid-IR for driving extreme nonlinearoptics in solids

Ekaterina Migal, Fedor Potemkin, and Viacheslav Gordienko

Doc ID: 308899 Received 10 Oct 2017; Accepted 20 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: We have developed the robust optical parametric amplifier (OPA) based on three AGS crystals pumping by Cr:Forsterite GW femtosecond laser system and generating 150-fs pulses in dual bands 1.6-2.0 µm (signal wave) and 3.5-5.5 µm (idler wave). Introducing negative prechirp to the pump, combined efficiency in two waves more than 10% was achieved with signal energy up to 110 μJ around 1.9 µm and idler energy up to 43 μJ in the vicinity of 4 μm. Operation parameters of the system (intensity up to 90 TW/cm2) makes OPA a promising tool for driving nonlinear optical phenomena including generation of optical harmonics and laser-induced extreme states of matter in solids and liquids. As a proof of principal, we generated high harmonics and sum frequencies in 5 mm thick polycrystalline ZnSe.

Flexible design method for freeform lenses with an arbitrary lens contour

Karel Desnijder, Peter Hanselaer, and Youri Meuret

Doc ID: 308074 Received 04 Oct 2017; Accepted 19 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: A method is presented that allows to design freeform lenses with an arbitrary contour in a flexible and robust manner. The method is based on the generation of two equi-flux grids representing the source and target beams, with two separate curl-free mappings from an equi-spatial rectangular grid. Because the source and target grids are generated independently from one another, one can map arbitrary complex source beams with a certain contour onto arbitrary complex target beams within another contour, with high convergence probability. The method is illustrated by calculating a triangular freeform lens that reshapes a triangular beam from a Lambertian source into a uniform pentagonal irradiance distribution on a target plane.

Efficient diode-pumped Er:KLu(WO4)2 laser at ~1.61 µm

Josep Maria Serres, Pavel Loiko, Venkatesan Jambunathan, Xavier Mateos, Vladimir Vitkin, Antonio Lucianetti, Tomas Mocek, Magdalena Aguilo, Francesc Diaz, Uwe Griebner, and Valentin Petrov

Doc ID: 309941 Received 25 Oct 2017; Accepted 19 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: We report on an efficient diode-pumped continuous-wave Erbium-doped monoclinic double tungstate laser. It is based on a 1 at.% Er3+:KLu(WO4)2 (Er:KLuW) crystal cut along the Ng optical indicatrix axis. The Er:KLuW microchip laser, diode-pumped at 0.98 µm, generates 268 mW at 1.610 µm with a slope efficiency of 30%. The output is linearly polarized (E || Nm) and the laser beam is nearly diffraction-limited. Spectroscopic properties of Er3+ in KLuW are also presented. The maximum σSE = 3.0×10-20 cm2 is at ~1.535 µm for E || Nm. The microchip Er:KLuW laser outperforms the commercial Er,Yb:glass.

Wavelength-Modulated Planar Laser-Induced Fluorescence for Imaging Gases

Garrett Mathews and Christopher Goldenstein

Doc ID: 308901 Received 12 Oct 2017; Accepted 19 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: This work presents the development of wavelength-modulated planar laser-induced fluorescence (WM-PLIF) and its initial application to infrared imaging of carbon monoxide in a laminar flame. A continuous-wave quantum-cascade laser producing 50 mW near 4.8 μm was injection-current modulated at 1 kHz and scanned across the P(20) transition of CO at 20 Hz. The corresponding infrared-laser-induced fluorescence was imaged orthogonal to the laser sheet using a high-speed IR camera operating at a frame rate of 28 kFPS, and digital lock-in detection of the WM-PLIF 1st-harmonic signal (S_F,1f) was performed to provide high-fidelity, background-free imaging of CO with a measurement bandwidth of 100 Hz. Images of the peak-S_F,1f signal are presented for a laminar CO-H_2 diffusion flame in air at atmospheric pressure. We demonstrate that this technique is sensitive enough to image nascent CO in flames and present a strategy for simulating the WM-PLIF harmonic signals.

Photo-Bleaching Mechanism of BAC-Si in Bismuth/Erbium Co-Doped Optical Fiber

Mingjie Ding, Jie FANG, Yanhua Luo, Wenyu WANG, and Gang-Ding Peng

Doc ID: 308104 Received 02 Oct 2017; Accepted 18 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: Photo-bleaching of silica related bismuth active center (BAC-Si) in bismuth/erbium co-doped optical fiber is investigated.By analyzing dynamic spectral characteristics of BAC-Si, the photo-bleaching of BAC-Si is linked to the escape of an excited electron from the bismuth site in BAC-Si.This mechanism of BAC-Si bleaching linked to an escaping excited electron is further confirmed with both the photo-bleaching experiments by different laser pump wavelengths and a potential energy model describing the loss of an excited electron.In addition, the temperature effect on the photo-bleaching, which is in good agreement with the above findings, is observed and discussed.

Modeling the sensitivity dependence of silicon-photonics-based ultrasound detectors

Shai Tsesses, Daniel Aronovich, Assaf Grinberg, Evgeny Hahamovich, and Amir Rosenthal

Doc ID: 307071 Received 13 Sep 2017; Accepted 17 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: With recent advances in optical technology, interferometric sensing has grown into a highly versatile approach for ultrasound detection, with many interferometric detectors relying on optical waveguides to achieve high levels of sensitivity and miniaturization. In this letter, we establish a practical model for assessing the sensitivity of silicon-photonics waveguides to acoustic waves. The analysis is performed for different polarizations, waveguide dimensions, and acoustic wave types. Our model was validated experimentally, by measuring the sensitivities of the two polarization modes in a silicon strip waveguide. Both the experimental results and theoretical prediction show that the TM polarization achieves a higher sensitivity and suppression of surface acoustic waves compared to the TE polarization.

Characterization of two ultrashort laser pulses using interferometric imaging of self-diffraction

Christoph Leithold, Jan Reislöhner, Holger Gies, and Adrian Pfeiffer

Doc ID: 307026 Received 12 Sep 2017; Accepted 16 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: Non-collinear pulse characterization methods can be applied to over-octave spanning waveforms, but geometrical effects in the nonlinear medium like beam smearing and critical sensitivity to beam alignment hinder their accurate application. Here, a method is introduced for the temporal and spatial characterization of two pulses by interferometric, spectrally resolved imaging of self-diffraction. Geometrical effects are resolved by the method and therefore do not limit the accuracy. Two methods for quantitative pulse retrieval are presented. One method is analytical and very fast, the other method is iterative and more robust if applied to noisy data.

Experimental study of the mode instabilities onset threshold in high power FA-LPF lasers

Marie-Alicia Malleville, Romain Dauliat, Aurélien Benoit, Baptiste Leconte, dia darwich, Rémi du Jeu, Raphael Jamier, Kay Schuster, and Philippe Roy

Doc ID: 308250 Received 29 Sep 2017; Accepted 16 Nov 2017; Posted 16 Nov 2017  View: PDF

Abstract: We report here on an experimental investigation of the temporal behavior of transverse mode instabilities into “Fully Aperiodic Large-Pitch Fibers” (FA-LPFs) operated in high-power CW laser configuration. To ensure an effective transverse single-mode emission into FA-LPFs, a perfect index-matching between the active core and the background cladding materials (∆n=0) is required. The original design of such fibers enables an effective transverse single-mode emission by strengthening the HOMs delocalization out of the gain region even for high heat load levels, consequently leading to the improvement of the beam spatial quality. The study was conducted over fibers of various gain region diameters – from 58 to 100 µm for a refractive index mismatch ∆n of about +8×10-5. The emitted beam is characterized using both M² measurements and time traces to study the changeover of a stable temporal behavior to an unstable one.

Off-axis tilt compensation in common-path digital holographic microscopy based on hologram rotation

Dingnan Deng, Weijuan Qu, Wenqi He, Yu Wu, Xiaoli Liu, and Xiang Peng

Doc ID: 304385 Received 14 Aug 2017; Accepted 16 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: We present a simple and effective compensation method for the off-axis tilt in common-path digital holographic microscopy (CPDHM) by introducing a rotating operation on the hologram. The proposed method mainly requires a digital reference hologram (DRH) which is a rotation version of the original one, it’s assumed to be easy to obtain by rotating the specimen’s hologram 180°. In this way, the off-axis tilt could be removed by subtracting the retrieved phase of DRH from the retrieved phase of original hologram, but without any complex spectrum centering judgement, fitting procedures or prior knowledge of the system. This highly automatic and efficient performance makes our approach available for real-time quantitative phase imaging (QPI). Some experimental results about a micro-lens array and a phase plate are provided to demonstrate the feasibility and effectiveness of the proposed method.

Kilohertz binary phase modulator for pulsed laser sources using a digital micromirror device

Maximilian Hoffmann, Ioannis Papadopoulos, and Benjamin Judkewitz

Doc ID: 309467 Received 19 Oct 2017; Accepted 16 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: The controlled modulation of an optical wavefront is required for aberration correction, digital phase conjugation or patterned photostimulation. For most of these applications it is desirable to control the wavefront modulation at the highest rates possible. The digital micromirror device (DMD) presents a cost-effective solution to achieve high-speed modulation and often exceeds the speed of the more conventional liquid crystal spatial light modulator, but is inherently an amplitude modulator. Furthermore, spatial dispersion caused by DMD diffraction complicates its use with pulsed laser sources, such as those used in nonlinear microscopy. Here we introduce a DMD-based optical design that overcomes these limitations and achieves dispersion-free high-speed binary phase modulation. We show that this phase modulation can be used to switch through binary phase patterns at the rate of 20 kHz in two-photon excitation fluorescence applications.

Effects of defocus and other quadratic errors on OTF

Kevin Liang and Miguel Alonso

Doc ID: 309409 Received 18 Oct 2017; Accepted 15 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: Even for the simplest nontrivial aberration, defocus, and for a circular pupil, there is no theoretical closed-form expression for the optical transfer function (OTF). By using a simple approximation for the error at the pupil, we provide a simple yet accurate approximation for the OTF of a defocused system. We then generalize this approach to generic quadratic aberrations, including astigmatism.

Radiation Induced-Birefringence Variations in Polarization Maintaining Fibers

Yuanhong Yang, Hui Li, Lin Lu, Fuling Yang, and Wei Jin

Doc ID: 308149 Received 29 Sep 2017; Accepted 14 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: Gamma radiation induced birefringence (RIB) variations in a solid core photonic crystal polarization maintaining fiber (Pc-PMF) and a Panda PMF (Pa-PMF) are investigated. Experiments show that the birefringence of the fibers changes approximately linearly with radiation dose over the range from 0 to 400 Krad(Si), with negative slope coefficients of 8.91×10¯¹⁰/Krad(Si) and 4.38×10¯⁹/Krad(Si)for the Pc-PMF and Pa-PMF, respectively. Models of RIB variations for the two fibers are established and the theoretical results agree well with the experimental ones

The Variable Stripe Length method: influence of stripe lengths choice on measured optical gain

Luis Cerdán

Doc ID: 310025 Received 27 Oct 2017; Accepted 14 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: The Variable Stripe Length (VSL) method is a very popular tool to measure the optical gain in thin film active devices. However, along the last decade experimental and theoretical evidences have been reported that cast doubts upon its reliability and that seriously discourage its application. Continuing in the path of finding new arguments against its use, this letter soundly demonstrates that the particular choice of stripe lengths in the VSL measurements profoundly influences the optical gains retrieved by this method. Thus, a single set of VSL data may render gain values differing tens of cm-1. The observed gain variability is ascribed to a combination of unavoidable experimental noise and incorrect assumptions in the analytical treatment (small-signal approximation).

Experimental Generation of Linearly Chirped 350 GHz-band Pulses with beyond 60 GHz Bandwidth

Hangkai Zhang, Shiwei Wang, Shi Jia, Xianbin Yu, Xiaofeng Jin, Shilie Zheng, Hao Chi, and Xianmin Zhang

Doc ID: 306548 Received 07 Sep 2017; Accepted 13 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: We present in this paper experimental generation of linear frequency modulated (LFM) THz pulses with large bandwidth by using an optical interferometer based photonic scheme and cutting-edge THz transceiver technology. The LFM pulses exhibiting a bandwidth in excess of 60 GHz centered at 350 GHz are successfully generated in the experiment, which represents the first demonstration of large time-bandwidth products (TBWP) in the THz region above 300 GHz, to the best of our knowledge. The achieved TBWP of up to 527 features a range resolution better than 1 cm and has great potential in many prospective applications such as high resolution radar sensing and imaging.

Multilayered analog optical differentiating device: performance analysis on structural parameters

Wenhui Wu, Wei Jiang, Jiang Yang, Shaoxiang Gong, and Yungui Ma

Doc ID: 307048 Received 13 Sep 2017; Accepted 13 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: Analogy optical devices with the function of mathematical computation have recently gained strong research interests due to the potential application as accelerating hardware in traditional electronic computers. The performance of these wavefront-processing devices is primarily decided by the accuracy of the engineered angular scattering spectra usually using artificial optical structures. In this paper, we address this issue through the performance analysis of an analog second-order optical differentiator made of dielectric (Si-SiO2) multilayer films that enable analytical discussions and also a combined design. The performance could be optimized according to the Fourier spectrum width of the incident light whose wavefront represents the input function. Based on this, we propose different optical differentiating devices that work for different wave input conditions. Rescaling of the Fourier spectrum intensity is suggested to enhance the fabrication and measurement error tolerance of the device. The minimum number of multilayers is also discussed in order to improve the practical feasibility. The current results are thought instrumental in guiding the design and implementation of analogy optical computation devices.

Phase transition through the splitting of self-dual spectral singularity in optical potentials

Vladimir Konotop and Dmitry Zezyulin

Doc ID: 305835 Received 28 Aug 2017; Accepted 13 Nov 2017; Posted 16 Nov 2017  View: PDF

Abstract: We consider optical media which feature antilinear symmetries. We show that: (i) spectral singularities of such media (if any) are always self-dual, i.e., correspond to CPA-lasers; (ii) under the change of a system's parameter the self-dual spectral singularity may split into a pair of isolated complex conjugate eigenvalues, which corresponds to an unconventional and overlooked in the most of previous studies scenario of the phase transition (known as PT-symmetry breaking in systems obeying parity-time symmetry); (iii) if the antilinear symmetry is local, i.e., does not involve any spatial reflection, then no spectral singularity is possible. Our findings are illustrated with several examples including a PT-symmetric bilayerand other complex potentials discussed in recent literature.

Diffraction symmetry of binary Fourier elements with feature sizes on the order of the illumination wavelength and effects of fabrication errors

Kevin Heggarty, Julien LE MEUR, Andreas Bacher, patrick Meyrueis, and Giang-Nam Nguyen

Doc ID: 297604 Received 08 Jun 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: When building spot array binary Fourier Diffractive Optical Elements (DOEs) having feature sizes on the order of the wavelength, we noticed remarkable variations in the experimental diffraction efficiency compared to the simulation results. Even with the use of a high-cost Electron Beam Lithography and the rigorous Fourier Modal Method simulations, there appear to be no publications, to our knowledge, showing close agreement in diffraction efficiency between simulation and experimental results. In this letter, we show that the diffraction symmetry of binary Fourier DOEs can be an efficient and consistent metric for evaluating the limit of the Thin Element Approximation and the effects of fabrication errors.

Direct writing of plane-by-plane tilted fiber Bragg gratings using a femtosecond laser

Andreas Ioannou, Antreas Theodosiou, Christophe Caucheteur, and Kyriacos Kalli

Doc ID: 307520 Received 21 Sep 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: In this letter, we report a flexible, plane-by-plane direct write inscription method for the development of tailored, tilted fiber Bragg gratings (TFBGs) using a femtosecond laser. Compared to UV- or femtosecond-laser inscription based on phase masks, interferometric or point by point methods, the presented approach is far more flexible and offers several advantages. Laser inscription is made through the fiber coating while the grating planes are controlled to minimize birefringence, with precise control over the wavelength location and strength of cladding modes. 10th order gratings were produced in the C+L bands so that higher order gratings could be studied at shorter wavelengths. In particular, we show that the refractometric sensitivity depends on the grating order, ranging from ~28 nm/RIU at ~1510 nm to ~13 nm/RIU at ~1260 nm.

Widely tunable optical parametric oscillation in a Kerr microresonator

Noel Sayson, Karen Webb, Stephane Coen, Miro Erkintalo, and Stuart Murdoch

Doc ID: 308086 Received 27 Sep 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: We report on the first experimental demonstration of widely-tunable parametric sideband generation in a Kerr microresonator. Specifically, by pumping a silica microsphere in the normal dispersion regime, we achieve the generation of phase-matched four-wave mixing sidebands at large frequency detunings from the pump. Thanks to the role of higher-order dispersion in enabling phase matching, small variations of the pump wavelength translate into very large and controllable changes in the wavelengths of the generated sidebands: we experimentally demonstrate over 720 nm of tunability using a low-power continuous-wave pump laser in the C-band. We also derive simple theoretical predictions for the phase-matched sideband frequencies, and discuss the predictions in light of thediscrete cavity resonance frequencies. Our experimentally measured sideband wavelengths are in very good agreement with theoretical predictions obtained from our simple phase matching analysis.

Partially coherent diffraction-free vertex beams with Bessel-mode structure

Andrey Ostrovsky, Joaquín García, Carolina Rickenstorff, and Miguel Angel Olvera

Doc ID: 308573 Received 04 Oct 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: A new family of partially coherent beams carrying optical vortices is introduced. Any member of this family represents an incoherent superposition of fully coherent Bessel modes with the same helical wave front and is notable for its diffraction-free propagation. It is shown analytically and experimentally that such beams can be approximately generated in the Fourier-transforming optical system with a computer-controlled liquid-crystal spatial light modulator.

Hilbert's Hotel in polarization singularities

Gregory Gbur and yangyundou wang

Doc ID: 308893 Received 11 Oct 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: We demonstrate theoretically how the creation of polarization singularities by the evolution of a fractional nonuniform polarization optical element involves the peculiar mathematics of countably infinite sets in the form of ``Hilbert's Hotel.' Two distinct topological processes can be observed depending on the structure of the fractional optical element.

Raman Dissipative Soliton Fiber Laser Pumped by an ASE Source

Weiwei Pan, Lei Zhang, Jiaqi Zhou, Xuezong Yang, and Yan Feng

Doc ID: 309046 Received 13 Oct 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: Mode locking of Raman fiber laser with an amplified spontaneous emission pump source is investigated for performance improvement. Raman dissipative solitons with pulse duration of 48 ps at a repetition rate of 2.47 MHz are generated by utilizing nonlinear polarization rotation and all-fiber Lyot filter. A signal to noise ratio as high as 85 dB is measured in radio-frequency spectrum, which suggests excellent temporal stability. Multiple pulse operation with unique random static distribution is observed for the first time at higher pump power in mode locked Raman fiber lasers.

Nonlinearity-aware 200-Gbit/s discrete multi-tone transmission for C-band short-reach optical interconnects with a single packaged EML

Lu Zhang, Xuezhi Hong, Xiaodan Pang, Oskars Ozolins, Aleksejs Udalcovs, Richard Schatz, Changjian Guo, Junwei Zhang, FREDRIK NORDWALL, Klaus Engenhardt, Urban Westergren, Sergei Popov, GUNNAR JACOBSEN, shilin xiao, Weisheng Hu, and Jiajia Chen

Doc ID: 306205 Received 01 Sep 2017; Accepted 13 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: We experimentally demonstrate the transmission of 200-Gbit/s discrete multi-tone (DMT) at soft-FEC limit in an intensity-modulation direct-detection system with a single C-band packaged distributed feedback laser and traveling-wave electro absorption modulator (DFB-TWEAM), digital-to-analog converter (DAC) and photodiode. The bits and power loaded DMT signal is transmitted over 1.6 km standard single mode fiber (SSMF) with a net rate of 166.7-Gbit/s, achieving an effective electrical spectrum efficiency of 4.93 bit/s/Hz. Meanwhile, net rates of 174.2-Gbit/s and 179.5-Gbit/s are also demonstrated over 0.8km SSMF and in optical back-to-back case, respectively. The feature of the packaged DFB-TWEAM is presented. The nonlinearity-aware digital signal processing algorithm for channel equalization is mathematically described, which improves the signal-to-noise ratio up to 4 dB.

Chirped-pulse-based broadband RF channelization implemented by mode-locked laser and dispersion

Wenhui Hao, Yitang Dai, FEIFEI YIN, Yue Zhou, Jianqiang Li, Jian Dai, Wangzhe Li, and Kun Xu

Doc ID: 307824 Received 25 Sep 2017; Accepted 13 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: Based on mode-locked laser and dispersion, a wideband radio frequency (RF) channelized receiver that can easily support hundreds of channels is proposed. By mixing a long-duration chirped pulse train and its own delayed copy, an equivalent RF local oscillation (LO) is produced which can down-convert the modulated signal to zero-intermediate-frequency (IF). The LO frequency can be changed by simply setting the delay between the two paths. Channelized receiving of broadband RF signals can be realized by parallel delay line arrays. Meanwhile, the using of in-phase/quadrature (I/Q) demodulation avoids the extra optical or electrical filtering as well as image interference. A receiver with channel spacing of 100 MHz, covering spectrum from DC to 18.4 GHz is experimentally demonstrated. The performances including signal-to- noise ratio (SNR), frequency response, spurious-free dynamic range (SFDR) and image rejection are analyzed.

Detuned Brillouin Amplification of OTDR Signals With Enhanced Signal-to-Noise Ratio

Egor Liokumovitch, Daniel Gotliv, and Shmuel Sternklar

Doc ID: 308043 Received 26 Sep 2017; Accepted 13 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: The technique known as external Brillouin amplification of Rayleigh scattering (eBARS) is characterized in the detuning regime. When employed as an amplifier of OTDR signals, it is shown that the SNR is significantly improved for optimum pump-Stokes detuning, leading to enhanced nanostrain sensitivity. This effect is due to the Brillouin bandwidth dependence on the Stokes power.

All-fiber 2-order optical vortex generation based on strong modulated long-period grating in 4-mode fiber

Wu Hang, She Gao, Bingsen Huang, Yuanhua Feng, xincheng huang, Weiping Liu, and Zhaohui Li

Doc ID: 308683 Received 10 Oct 2017; Accepted 13 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: We propose an effective all-fiber method to generate high-order optical vortex (OV) via twisting a strong modulated long period fiber grating (LPFG) written in a four-mode fiber (4MF). With special design and optimization of the procedures of CO2-laser irradiation, an LPFG with strong period deformation is achieved in the 4MF. Based on this LPFG, we can directly convert the linear polarization (LP) fiber fundamental mode (LP01) to the high order LP core mode (LP21) with efficiency of 99.7 percent, and then, transform the LP21 mode into high-order OV mode (±2 order). It is the first time, to the best of our knowledge, ±2-order OV modes are experimentally generated with just one fiber grating in an all-fiber-system. © 2017 Optical Society of America

Tens-of-Hz narrow-linewidth laser based on Stimulated Brillouin and Rayleigh scattering

Shihong Huang, Tao Zhu, Guolu Yin, Tianyi Lan, Ligang Huang, Fuhui Li, Yongzhong Bai, Dingrong Qu, Xianbin Huang, and FENG QIU

Doc ID: 305751 Received 28 Aug 2017; Accepted 13 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: We proposed and demonstrated a linewidth compression method of laser based on stimulated Brillouin scattering (SBS) and Rayleigh backscattering structure (RBS). The relationship between the output SBS laser linewidth and the input pump linewidth was studied theoretically and experimentally. It is shown that the narrower linewidth of the pump laser leads to the narrower bandwidth of the SBS gain, and finally the bandwidth of the SBS will tend to its intrinsic value as the linewidth of pump laser narrower than 10 kHz, then the linewidth of SBS fiber ring laser would tend to 200 Hz. In order to further reduce its linewidth with low cost, RBS and a simple dual-cavity feedback structure were added, and finally ~75-Hz narrow-linewidth laser with a side-mode suppression ratio of 70 dB was obtained.

Homographically generated light-sheets for themicroscopy of large specimens

Craig Russell, Eric Rees, and Clemens Kaminski

Doc ID: 304060 Received 29 Sep 2017; Accepted 12 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: We compare the performance of linear and nonlinear methods for aligning the excitation and detection planes throughout large specimen volumes in digitally scanned light sheet microscopy. An effective non-linear method involves registering four corner extrema of the imaging volume using a projective transform. We show this improves on the light collection efficiency of a 3-point affine registration by an average of 42% over a typical specimen volume, but increasingly higher-order corrections provide more modest returns. The accuracy of illumination/detection registration methods are now very pertinent to biological research in view of current trends towards imaging large or expanded samples, at depth, with diffraction limited resolution.

Jones matrix microscopy from a single shot measurement

M. Sreelal, VINU RV, and Rakesh Singh

Doc ID: 309464 Received 18 Oct 2017; Accepted 12 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: Quantitative measurement of Jones matrix elements is crucial for the study of light polarization with wide range of applications. Here, we propose and experimentally demonstrate a novel method of Fourier space sharing to determine spatially resolved all four elements of the Jones matrix from a single intensity frame. This is achieved by applying holography approach and making use of two triangular polarization Sagnac interferometers in the sample and reference arms. The proposed technique is flexible to adjust carrier frequencies in order to meet the varying demand of different anisotropic samples. Jones matrix microscopy system is developed and applied for transparent samples. Experimental implementation of the proposed technique is demonstrated by determining the Jones matrix elements of commercially available known samples and liquid crystal droplets.

Two-mode surface plasmon lasing in hexagonal arrays

Vasco Tenner, Michiel de Dood, and Martin van Exter

Doc ID: 297731 Received 25 Aug 2017; Accepted 12 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We demonstrate surface-plasmon lasing in hexagonal metal hole arrays with a semiconductor gain medium. The device can be tuned between two laser modes, with distinct wavelengths, spatial distributions and polarization patterns by changing the size of the optically pumped area. One of the modes exhibits a six-fold polarization pattern, while the mode observed for larger pump spots has a rotationally symmetric polarization pattern. We explain the mode tuning by the differences of in-plane and radiative out-of-plane losses of the modes. The spatial and polarization properties of the modes are conveniently described by a sum of vectorial OAM beams with orbital, spin and total angular momentum j = l+s.

Topological cascade laser for frequency combgeneration in PT -symmetric structures

Laura Pilozzi and Claudio Conti

Doc ID: 307825 Received 27 Sep 2017; Accepted 12 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: The cascade of resonant PT -symmetric topologicalstructures is shown to emit laser light with a frequencycombspectrum. We consider optically active topologicallattices supporting edge-modes at regularly spacedfrequencies. When the amplified resonances in the PT -broken regime match the edge modes of the topologicalgratings, we predict the emission of discrete laserlines. A proper design enables to engineer the spectralfeatures for specific applications. Topological protectionmakes the system very well suited for a novel generationof compact frequency comb emitters for spectroscopy,metrology and quantum information.

Ultra-compact polarization-independent directional couplers utilizing subwavelength structures

Yaocheng Shi and Hongnan Xu

Doc ID: 309214 Received 16 Oct 2017; Accepted 11 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: Ultra-compact polarization-independent directional couplers are proposed and demonstrated on the Silicon-On-Insulator (SOI) platform. By using the subwavelength structures in the coupling region, the coupling strength is greatly enhanced only for TE polarization, so that the coupling strength could be equivalent between TE and TM polarizations. Both complete coupling and 3-dB splitting have been demonstrated. The polarization independent coupling length is only ~ 3.75 μm. The measured excess losses and polarization dependence losses are < ~ 1 dB and < ~ 0.5 dB.

A self-tuning optical resonator

Joanna Zielinska and Morgan Mitchell

Doc ID: 309076 Received 13 Oct 2017; Accepted 10 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We demonstrate a nonlinear optical resonator that tunes itself onto resonance with an input beam. In a monolithic Fabry-Perot cavity implemented in rubidium-doped periodically-poled potassium titanyl phosphate, an intensity-dependent refractive index produces line-pulling by multiple free-spectral ranges (FSRs). In this condition, the cavity passively maintains optical resonance in the face of FSR-scale excursions of the drive laser frequency: when one resonant operating-point becomes unstable, the resonator rapidly transitions to another resonant operating point. We demonstrate stable second-harmonic generation with no active feedback to laser or cavity. The self-tuning effect appears to be supported by a very strong, previously unreported optical nonlinearity.

Single travelling wave-like Fabry-Perot resonator based add-drop filters for wavelength multiplexing

Qingzhong Huang, Qiang Liu, and Jinsong Xia

Doc ID: 312557 Received 03 Nov 2017; Accepted 10 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: We have proposed and studied a novel channel add-drop filter (ADF) based on a single Fabry-Perot resonator. The resonator consists of two mode-conversion Bragg grating reflectors separated by a wide waveguide that laterally coupled to two narrow waveguides. It behaves like a travelling-wave resonator where fields are coupled to the buses in one direction. Compact and narrowband ADFs are achieved with dropping efficiencies higher than 95%, as shown by the three-dimensional finite-difference time-domain simulations. In addition, the proposed device is applied to realize an eight-channel add-drop multiplexer in the C-band by cascading the ADFs with adjusted channel wavelengths.

Exploring the self-mode-locking of the 2-μm Tm:YAG laser with suppression of the self-pulsing dynamic

Chun-Yu Cho, Yung-Fu Chen, Zhang Ge, Weidong Chen, and Hsing-Chih Liang

Doc ID: 309807 Received 23 Oct 2017; Accepted 10 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: A continuous-wave (cw) self-mode-locked Tm:YAG laser at 2015 nm is successfully demonstrated by suppressing the self-pulsing behavior. By using rate equations to simulate the laser temporal dynamic, the theoretical analysis indicates that the reabsorption-induced self-pulsing for the Tm:YAG laser can be suppressed with sufficient pump power. It is experimentally confirmed that at absorbed powers higher than 6 W, the self-pulsing can be eliminated and a cw self-mode-locked pulses is generated instead of the Q-switched mode locking. At an absorbed power of 6.8 W, the output power of the self-mode-locked Tm:YAG laser reaches 1.22 W with corresponding pulse duration of 3 ps and a repetition rate 3.376 GHz.

All-fiber interferometer-based repetition-rate stabilization of mode-locked lasers to 10¯¹⁴-level frequency instability and 1-fs-level jitter over 1-s

Dohyeon Kwon and Jungwon Kim

Doc ID: 309718 Received 30 Oct 2017; Accepted 09 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We report on all-fiber Michelson interferometer-based repetition-rate stabilization of femtosecond mode-locked lasers down to 1.3×10¯¹⁴ frequency instability and 1.4-fs integrated jitter in 1-s time scale. The use of a compactly packaged 10-km-long SMF-28 fiber link as a timing reference allows the scaling of phase noise down to -80 dBc/Hz at 1-Hz Fourier frequency. We also tested a 500-m-long low-thermal-sensitivity fiber as a reference and found that, compared to standard SMF-28 fiber, it can mitigate the phase noise divergence by ~10 dB/dec in the 0.1 – 1 Hz Fourier frequency range. These results suggest that the use of a longer low-thermal-sensitivity fiber may achieve sub-fs integrated timing jitter with sub-10¯¹⁴–level frequency instability in repetition-rate by a simple and robust all-fiber-photonic method.

Steering optical comb frequencies by rotating the polarization state

Yanyan Zhang, Xiao-Fei Zhang, Lulu Yan, Pan Zhang, bingjie rao, Wei Han, wenge guo, Shou-Gang Zhang, and Haifeng Jiang

Doc ID: 310117 Received 30 Oct 2017; Accepted 09 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We demonstrate a new approach to steer the frequencies of a nonlinear-polarization-rotation mode-locked laser, where a specially designed intra-cavity electrooptic modulator tunes the polarization state of the laser signal. Not only does this approach result in the broadband associated with high performance, but it also results in large dynamic range associated with good robustness. Our experimental results show that frequency control dynamic ranges are at least one order of magnitude than these of the previous ultra-fast frequency control techniques, reaching hundreds hertz and hundreds megahertz for repetition rate ( fr) and carrier envelop offset frequency ( fceo), respectively.

Experimental demonstration of critical coupling of whispering gallery mode cavities on Bloch surface wave platform

Babak Vosoughi Lahijani, Habib Badri Ghavifekr, Richa Dubey, Myun-Sik Kim, Ismo Vartiainen, Matthieu Roussey, and Hans Peter Herzig

Doc ID: 308726 Received 06 Oct 2017; Accepted 09 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We experimentally demonstrate critical coupling of whispering gallery mode (WGM) disk resonators implemented on a Bloch surface wave platform using scanning near-field optical microscopy. The studied structure is a 60-nm-thick TiO2 WGM disk cavity (radius of 100 μm) operating within the C-band telecommunication wavelengths. An extinction ratio of 26 dB and a quality factor of 2,200 are measured. Such a high extinction ratio verifies the critical coupling of the WGM resonator. This result paves the way to planar optical signal processing devices based on the proposed geometry, for which critical coupling condition is a guarantee of optimum performance.

Direct write micro/nano optical fibers by near-field melt electrospinning

Qinnan Chen, Xuecui Mei, Zhe Shen, Dezhi Wu, Yang Zhao, Lingyun Wang, Xiaojun Chen, Gonghan He, zhe yu, Ke Fang, and Daoheng Sun

Doc ID: 308151 Received 29 Sep 2017; Accepted 09 Nov 2017; Posted 09 Nov 2017  View: PDF

Abstract: A simple fabrication method of micro/nano optical fibers (MNOFs) by near-field melt electrospinning (NMES) was proposed in this paper. Single fibers with diameter ranging from 500nm to 6μm were direct written by near-field electrospinning melt Poly(methyl methacrylate) (PMMA). The morphology and transmission characteristics of single PMMA MNOFs were experimentally measured. Results showed that PMMA MNOFs have the advantages of smooth surfaces, uniform diameters, and low loss. As an example of one-step fabrication for MNOF devices, a planar helical MNOF structure was direct written and optically characterized. To demonstrate the versatility of NMES process, combined with microfluidic technique, a liquid refractive index sensing chip has been fabricated and tested. Our work has already showed the proposed fabrication method has great potential in direct-writing patterned optical devices and heterogeneous integrated devices.

Single-shot, real-time carrier-envelope phase measurement and tagging based on stereographic above-threshold ionization at short-wave Infrared wavelengths

Yinyu Zhang, Philipp Kellner, Daniel Adolph, DANILO ZILLE, Philipp Wustelt, Daniel Würzler, Slawomir Skruszewicz, Max Möller, A SAYLER, and Gerhard Paulus

Doc ID: 308653 Received 11 Oct 2017; Accepted 09 Nov 2017; Posted 09 Nov 2017  View: PDF

Abstract: A high-precision, single-shot and real-time carrier-envelope phase (CEP) measurement at 1.8 µm laser wavelength based on stereographic photoelectron spectroscopy is presented. A precision of the CEP measurement of 120 mrad for each and every individual laser shot for a 1-kHz pulse train with randomly varying CEP is demonstrated. Simultaneous to the CEP measurement, the pulse lengths are characterized by evaluating the spatial asymmetry of the measured above-threshold ionization (ATI) spectra of Xenon and referenced to a standard pulse-duration measurement based on frequency-resolved optical gating (FROG). The validity of the CEP measurement is confirmed by implementing phase-tagging for a CEP-dependent measurement of ATI in Xe with high energy resolution.

Great photoluminescence enhancement in Al-sputtered Zn0.78Mg0.22O films

YONGHUI ZHOU, Shanshan Chen, Xinhua Pan, and Zhizhen Ye

Doc ID: 309199 Received 17 Oct 2017; Accepted 08 Nov 2017; Posted 09 Nov 2017  View: PDF

Abstract: Zn0.78Mg0.22O thin films were grown on a-plane sapphire substrates by plasma-assisted molecular beam epitaxy. Compared with ZnO, the crystal quality of Zn0.78Mg0.22O thin films degrades significantly, which results in a low internal quantum efficiency (ηint). Besides improving the quality of Zn0.78Mg0.22O, an effective way to enhance the internal quantum efficiency and the UV emission of Zn0.78Mg0.22O by sputtering Al nanoparticles has been used. Taking advantage of the resonant coupling between UV emission of Zn0.78Mg0.22O film and Al nanoparticle surface plasmons (SPs), a 59-fold enhancement of the UV emission and a 3.5-fold enhancement of ηint have been achieved under the optimized sputtering time. Moreover, the enhancement ratio is stable after two months. It paves a facile way in fabricating high-efficiency UV optoelectronic devices.

Full-C-band Si Photonic Crystal Waveguide Modulator

Yosuke Terada, Keisuke Kondo, Ryotaro Abe, and Toshihiko Baba

Doc ID: 309778 Received 23 Oct 2017; Accepted 08 Nov 2017; Posted 09 Nov 2017  View: PDF

Abstract: The slow-light effect in silicon lattice-shifted photonic crystal waveguide (LSPCW) Mach-Zehnder modulators allows compact phase shifters while limiting the working spectrum Δλ. We optimized the structural parameters of the LSPCW and extended Δλ to cover the full C-band in exchange for moderately decreasing the group index ng. We obtained Δλ = 42 nm with ng = 8–9 in a fabricated device and observed 25-Gbps eye opening in the 200-μm modulator in the full C-band.

Design of nanowire-induced nanocavities in photonic crystal disks

Sylvain Sergent, Hideaki Taniyama, and Masaya Notomi

Doc ID: 308295 Received 26 Oct 2017; Accepted 08 Nov 2017; Posted 08 Nov 2017  View: PDF

Abstract: We propose a novel type of nanowire-induced nanocavity based on photonic crystal disks and we investigate its design by three-dimensional finite-difference time-domain calculations. We detail the confinement principle used in such a cavity and discuss the influence of geometric and material parameters on the cavity performance. We finally report on an optimized design presenting a quality factor Q = 7.2×10^4, a mode volume as small as Vm = 2.2 (λ/nrNW)^3 and a large confinement factor of the electric field energy in the NW Γ = 65%, which shows good prospects for the realization of efficient nanowire-based nanolasers operating in the ultraviolet and visible ranges.

A hybrid unidirectional meta-coupler for vertical incidence to a high-refractive-index waveguide in telecom wavelength

Chensheng Gong, Sailing He, and Jianhao Zhang

Doc ID: 308591 Received 16 Oct 2017; Accepted 08 Nov 2017; Posted 08 Nov 2017  View: PDF

Abstract: A hybrid unidirectional meta-coupler for vertical incidence to a high-refractive-index waveguide in telecom wavelength is demonstrated. Phase gradient plasmonic metasurfaces composed of periodic MIM structure are used for phase matching. Three designs are given for devices working around 0.85μm, 1.31μm and 1.55μm. The simulated coupling efficiencies are all around 70% and the 1 dB coupling bandwidths are 29nm, 82nm and 105nm, respectively. Back reflections in the waveguide are also estimated to be lower than 5%. Our approach paves the way for the applications of optical metasurfaces to planar lightwave.

Quantification of laser-induced damage growth using fractal analysisQuantification of laser-induced damage growth using fractal analysis

Matthieu Veinhard, Odile Bonville, Roger Courchinoux, Romain Parreault, Jean-Yves Natoli, and Laurent Lamaignère

Doc ID: 307217 Received 21 Sep 2017; Accepted 08 Nov 2017; Posted 09 Nov 2017  View: PDF

Abstract: Lateral and longitudinal laser damage growth under subsequent irradiations at 351 nm in the nanosecond range from micrometric to millimetric scales is presented herein. Atypical behavior has been observed, showing the growth in the longitudinal direction whereas the lateral growth does not evolve. We propose the use of fractal analysis to describe the evolution of the bulk damage morphology. Results indicate first a dependence between the damage fractal dimension and the laser parameters, such as the fluence and the pulse duration. Next, it seem from observations that the damage morphology modifications drive the growth rate changes.


Jinlong Zhang, han wu, Hongfei Jiao, Sven Schröder, Marcus Trost, Zhanshan Wang, and Xinbin Cheng

Doc ID: 308439 Received 03 Oct 2017; Accepted 07 Nov 2017; Posted 08 Nov 2017  View: PDF

Abstract: Light scattering in quarter-wave high reflection (QWHR) coatings with fully correlated interfaces was reduced by adding Fabry-Perot (FP) cavity structures on top of the multilayer. The properly designed FP cavity can induce destructive interference for fully correlated interfaces and reduce the scattering loss. Compared to QWHR coatings, adding one FP cavity could decrease the scattering at the near specular angles, and two FP cavities have the potential to reduce light scattering in a broad angular range. A low-scattering HR (LSHR) coating using two FP cavities has been realized to suppress light scattering omnidirectionally. The numerical scattering calculation illustrated that the total scattering loss of the LSHR was about two times less than that of the QWHR coatings. The measured angle resolved scattering of the LSHR coating showed a good correspondence to the numerical calculation although there exists small deviation in a limited angular range.

1.25 GHz sine wave gating InGaAs/InP single-photon detector with monolithically integrated readout circuit

Wen-Hao Jiang, Jianhong Liu, Y. Liu, Ge Jin, Jun Zhang, and Jian-Wei Pan

Doc ID: 304580 Received 10 Aug 2017; Accepted 07 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: InGaAs/InP single-photon detectors (SPDs) are the key devices for applications requiring near-infrared single-photon detection. Gating mode is an effective approach to synchronous single-photon detection. Increasing gating frequency and reducing size are important challenges for the design of such detector system. Here we present for the first time an InGaAs/InP SPD with 1.25 GHz sine wave gating using a monolithically integrated readout circuit (MIRC). The MIRC has a size of 15 mm × 15 mm and implements the miniaturization of quenching electronics for high-frequency sine wave gating. In the MIRC, low-pass filters and a low-noise radio frequency amplifier are integrated based on the technique of low temperature co-fired ceramic, which can effectively reduce the parasitic capacitance and extract weak avalanche signals. We then characterize the key parameters of InGaAs/InP SPD to verify the functionality of MIRC, and the SPD exhibits excellent performance with 27.5 % photon detection efficiency, 1.2 kcps dark count rate, and 9.1 % afterpulse probability at 2 K and 100 ns hold-off time. With this MIRC, one can further design miniaturized high-speed InGaAs/InP SPDs highly required for practical applications.

Refractionless propagation of discretized light

Stefano Longhi

Doc ID: 308819 Received 10 Oct 2017; Accepted 07 Nov 2017; Posted 09 Nov 2017  View: PDF

Abstract: Light refraction, i.e. the bending of the path of a light wave at the interface between two different dielectric media, is ubiquitous in optics. Refraction arises from the different speed of light and is unavoidable in continuous media according to Snell's Law. Here we show rather counterintuitively that omnidirectional refractionless propagation can be observed for discretized light crossing a tilted interface separating two homogeneous waveguide lattices.

Fiber-optic radio frequency transfer based on active phase noise compensation using a carrier suppressed double-sideband signal

Jiapeng Zhang, Guiling Wu, Tiancheng Lin, and Jianping Chen

Doc ID: 306605 Received 08 Sep 2017; Accepted 06 Nov 2017; Posted 08 Nov 2017  View: PDF

Abstract: In this letter, we propose a fiber-optic radio frequency (RF) transfer based on active phase noise compensation adopting a carrier suppressed double-sideband (CSDSB) signal. The forward CSDSB signal is generated based on the transmitted RF signal at the local site to discriminate from the backward RF signal. The forward and backward signals are transmitted over the same fiber with the same wavelength to guarantee the bidirectional propagation symmetry. The impact of backscattering is efficiently suppressed by electrical filtering at sites. A 1 GHz signal transfer over a 40 km optical link is performed in laboratory. The results show that the proposed scheme can improve the short term stability from 1.9e-13 /s to 3.9e-14 /s in contrast to the scheme with backscattering while reaching a long term stability of 2.0e-16 /10000s.

Perfect Broad-Band Invisibility in Isotropic Media with Gain and Loss

Farhang Loran and Ali Mostafazadeh

Doc ID: 305770 Received 28 Aug 2017; Accepted 06 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We offer a simple route to perfect omnidirectional invisibility in a spectral band of desired width which is based on the observation that in two dimensions a complex potential v(x,y) is invisible for incident plane waves with a wavenumber not exceeding a preassigned value α provided that its Fourier transform with respect to y, which we denote by $\tilde v(x,K_y)$, vanishes for $K_y ≤ 2α$. We can fulfil this condition for potentials modelling the permittivity profile of an optical slab. Such a slab is perfectly invisible for any transverse electric wave whose wavenumber is in the range [0,α]. Our results also apply to transverse magnetic waves propagating in a medium with a relative permittivity that is a smooth bounded function with a positive real part.

A photonics-based multi-function analog signal processor based on a polarization division multiplexing Mach-Zehnder modulator

Shilong Pan and Yamei Zhang

Doc ID: 304769 Received 18 Aug 2017; Accepted 06 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: A photonics-based multi-function analog signal processor based on an optical polarization division multiplexing (PDM) dual-parallel Mach-Zehnder modulator (DPMZM) is proposed and demonstrated, which can implement simultaneously photonic microwave phase shifting, up-/down-conversion and filtering with excellent tunability. An experiment is carried out. Down-converted and up-converted phase shifters with phases continuously tuned from -180 to 180 degree over 0-11 GHz and 11-33 GHz are implemented. Based on the frequency-mixed phase shifter, a 4-tap microwave photonic filter (MPF) that has the capability to select a frequency-mixed component is built. The proposed approach features multi-function, scalable independent channels, wide bandwidth and high tunability, which can find applications in beamforming networks, RF frontends, and radio over fiber systems.

Effects of defocus on the transfer function of coherence scanning interferometry

Rong Su, MATTHEW THOMAS, Richard Leach, and Jeremy Coupland

Doc ID: 304940 Received 17 Aug 2017; Accepted 06 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: Coherence scanning interferometry (CSI) offers three dimensional (3D) measurement of surface topography with high precision and accuracy. Defocus within the interferometric objective lens, however, is commonly present in CSI measurements, and reduces both the resolving power of the imaging system and the ability to measure tilted surfaces. This paper extends the linear theory of CSI to consider the effects of defocus on the 3D transfer function and the point spread function in an otherwise ideal CSI instrument. The results are compared with measurements of these functions in a real instrument. This work provides further evidence for the validity of the linear systems theory of CSI.

Spatiotemporal diffraction-free pulsed beams infree-space of the Airy and Bessel type

Nikolaos Efremidis

Doc ID: 305329 Received 22 Aug 2017; Accepted 06 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: We investigate the dynamics of spatiotemporal optical waves with one transverse dimension that are obtained as the intersections of the dispersion cone with a plane. We show that, by appropriate spectral excitations, the three different types of conic sections (elliptic, parabolic, and hyperbolic) can lead to optical waves of the Bessel, Airy, and modified Bessel type, respectively. We find closed form solutions that accurately describe the wave dynamics and unveil their fundamental properties.

On-chip Brillouin purification for frequency comb-based coherent optical communications

Amol Choudhary, Mark Pelusi, David Marpaung, Takashi Inoue, Khu Vu, Pan Ma, Duk-Yong Choi, Stephen Madden, Shu Namiki, and Benjamin Eggleton

Doc ID: 306263 Received 05 Sep 2017; Accepted 06 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: In this paper, we for the first time harness on-chip Brillouin scattering for narrowband amplification and spectral purification of frequency comb lines for coherent optical communications. A parametrically-generated optical frequency comb with a low carrier to noise power ratio was filtered through narrowband Brillouin amplification utilizing the same comb as the re-circulated optical pump. This was achieved on a photonic chip to enable successful transmission of an advanced modulation format signal: 64-level quadrature amplitude modulation (QAM). 96 Gigabits/second data was modulated on two polarizations on multiple comb-lines across 1532.9-1557.5 nm demonstrating the scalability of this concept for operation in wavelength division multiplexing applications. The small form-factor of the photonic chip reduces the polarization drifts when compared to optical fibers and paves the way for photonic integration.

On Babinet’s Principle and Diffraction Associated with an Arbitrary Particle

Bingqiang Sun, Ping Yang, George Kattawar, and Michael Mishchenko

Doc ID: 307984 Received 26 Sep 2017; Accepted 06 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: Babinet’s principle is widely used to compute the diffraction by a particle. However, the diffraction by a 3-D object is not totally the same as that simulated with Babinet’s principle. This letter uses a surface integral equation to exactly formulate the diffraction by an arbitrary particle and illustrates the condition for the applicability of Babinet’s principle. The present results may serve to close the debate on the diffraction formalism.

Generation of uniformly oriented in-plane magnetization with near-unity purity in 4π microscopy

Xiangping Li, Sicong Wang, and Yao-Yu Cao

Doc ID: 305222 Received 21 Aug 2017; Accepted 06 Nov 2017; Posted 09 Nov 2017  View: PDF

Abstract: In this Letter, we numerically demonstrate the all-optical generation of uniformly oriented in-plane magnetization with near-unity purity (more than 99%) under a 4π microscopic configuration. This is achieved through focusing two counter-propagating vector beams consisting of coherently configured linear and radial components. Based on the Richards and Wolf diffraction theory, constructive and destructive interferences of the focal field components can be tailored under the 4π configuration to generate high-purity uniformly polarized transverse and longitudinal electric-field components in the center of the focal region. Consequently, near-unity purity in-plane magnetization with a uniform orientation within the focal volume defined by the full width at half maximum can be created through the inverse Faraday effect. In addition, it reveals that the purity of the in-plane magnetization is robust against the numerical aperture of the focal lens. This result expands the flexibility of magnetization manipulations through light and holds great potentials in all-optical magnetic recording and spintronics.

Enhancement of bulk second-harmonic generation from silicon nitride films by material composition

Kalle Koskinen, Robert Czaplicki, Abdallah Slablab, Tingyin Ning, Artur Hermans, Bart Kuyken, Vinita Mittal, Ganapathy Senthil Murugan, Tapio Niemi, Roel G. Baets, and Martti Kauranen

Doc ID: 307991 Received 26 Sep 2017; Accepted 05 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: We present a comprehensive tensorial characterization of second-harmonic generation from silicon nitride films with varying composition. The samples were fabricated using plasma-enhanced chemical vapor deposition, and the material composition was varied by the reactive gas mixture in the process. We found a six-fold enhancement between the lowest and highest second-order susceptibility, with the highest value of approximately 5 pm/V from the most silicon-rich sample. Moreover, the optical losses were found to be sufficiently small (below 6 dB/cm) for applications. The tensorial results show that all samples retain in-plane isotropy independent of silicon content, highlighting the controllability of the fabrication process.

Micro-Scale Roughening of Glass Substrates Using Carbon Nanotube-Driven Templates for Enhancements in White Luminescence Characteristics

Jin Woo Jang, Oh Hyeon Kwon, Jun Sik Kim, Yuri Kim, and Yong Soo Cho

Doc ID: 308041 Received 27 Sep 2017; Accepted 05 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: A novel way of roughening the surface of a glass substrate using a carbon nanotube (CNT)-driven template is introduced to enhance white luminescence characteristics of a printed (Ba,Sr,Ca)2SiO4:Eu2+ yellow silicate phosphor layer. The distribution of closed pores in the template layer induces the selective etching and the micro-scale roughening. As a result, a substantial improvement of ~22.5% in the luminous efficacy was achieved when both sides of the substrate were roughened. This is attributed to the reductions of both the total internal reflection of rays at the glass–air interface and the specular reflection at the phosphor-glass interface.

A Fan-Beam Steering Device Using a Photonic Crystal Slow-Light Waveguide with Surface Diffraction Grating

Keisuke Kondo, Tomoki Tatebe, Shoji Hachuda, Hiroshi Abe, Fumio Koyama, and Toshihiko Baba

Doc ID: 309774 Received 23 Oct 2017; Accepted 05 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: Compact non-mechanical beam steering devices are desired not only for current common applications but also for advanced applications such as light detection and ranging. We use a Si photonic crystal slow-light waveguide with a diffraction grating, which radiates the guided mode to free space and steers a fan beam by sweeping the wavelength. Due to its large angular dispersion, slow light enhances the steering range without degrading the beam quality, resulting in more resolution points. We fabricated 600-μm devices and observed a ⁰ steering range and a beam divergence of 0. ⁰, which resulted in 100 resolution points.

Wavefront-sensing with a thin diffuser

Marc Guillon, Pascal Berto, and Herve Rigneault

Doc ID: 308993 Received 11 Oct 2017; Accepted 05 Nov 2017; Posted 09 Nov 2017  View: PDF

Abstract: We propose and implement a broadband, compact, and low-cost wavefront sensing scheme by simply placing a thin diffuser in the close vicinity of a camera. The local wavefront gradient is determined from the local translation of the speckle pattern. The translation vector map is computed thanks to a fast diffeomorphic image registration algorithm and integrated to reconstruct the wavefront profile. The simple translation of speckle grains under local wavefront tip/tilt is ensured by the so-called ``memory effect' of the diffuser. Quantitative wavefront measurements are experimentally demonstrated both for the few first Zernike polynomials and for phase-imaging applications requiring high resolution. We finally provided a theoretical description of the resolution limit that is supported experimentally.

All-optical control of ultrahigh-Q silica microcavities with iron oxide nanoparticles

Song Zhu, Lei Shi, Shixing Yuan, xinbiao xu, and Xinliang Zhang

Doc ID: 306923 Received 11 Sep 2017; Accepted 04 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: The first all-optical control scheme of ultrahigh-quality (Q)-factor silica microcavities, which can maintain their Q factors over 108 during the tuning process, is proposed and experimentally demonstrated. For silica microcavities, the resonance tunability is very important and also challenging for many applications. However, almost all previous works on resonance tuning deteriorate the Q factors of silica microcavities at different levels, and evidently these schemes are not suitable for applications in which ultrahigh Q factors are required. In this work, based on the proposed silica microbottle cavity and iron oxide nanoparticles, we realize all-optical control of the silica microcavity and maintain its Q factor of around 1.2108 during the tuning process. A tuning range of 85.9 GHz (0.68 nm) and a tuning sensitivity of 13.6 GHz/mW are obtained, and it is possible to realize full tunability by bridging the azimuthal free spectral range using six adjacent q-series modes. Moreover, all-optical control of the reflection spectrum is also carried out. This work will broaden the applications of ultrahigh-Q silica microcavities in nonlinear optics, microwave photonics, cavity optomechanics and cavity quantum electrodynamics.

High reflective Mo/Be/Si multilayers for the EUV lithography

Nikolay Chkhalo, Sergey Gusev, Andrei Nechay, Dmitri Pariev, Vladimir Polkovnikov, Nikolay Salashchenko, Franz Schäfers, Mewael Sertsu, Andrey Sokolov, Mikhail Svechnikov, and Dmitry Tatarsky

Doc ID: 306455 Received 07 Sep 2017; Accepted 03 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: The effect of Be interlayers on the reflection coefficients of Mo/Si multilayer mirrors in the EUV (extreme ultraviolet) region is reported. Samples were studied using a laboratory and synchrotron based reflectometry, and high resolution transmission electron microscopy. The samples under study have reflection coefficients above 71% at 13.5 nm and more than 72% at 12.9 nm in normal incidence mode. Calculations show that by optimizing the thickness of the Be interlayer, it should be possible to increase the reflection coefficient by another 0.5-1%. These results are of considerable interest for EUV lithography.

High performance Ge-on-Si photodetector with optimized DBR location

Zhiping Zhou and Jishi Cui

Doc ID: 308936 Received 12 Oct 2017; Accepted 03 Nov 2017; Posted 09 Nov 2017  View: PDF

Abstract: We investigated the Ge-on-Si photodetectors’ performance enhancement by optimizing the photodetector length, therefore, the location of the Distributed Bragg reflector (DBR). Since the unabsorbed signal light in the photodetector is oscillating between the germanium and silicon layers, but the DBR is on the silicon layer, the optimized location of the DBR will result shorter devices, with increased bandwidth, reduced dark current, and maintaining the responsivity. The 5 μm long photodetector with optimized DBR location shows responsivity of 0.72 A/W, and at least 31.7 GHz 3 dB bandwidth. The dark current is only 7 nA.

Non-invasive characterization of optical fibers

Sören Schmidt, Tobias Tieß, Siegmund Schroeter, Anka Schwuchow, Matthias Jaeger, Hartmut Bartelt, Andreas Tünnermann, and Herbert Gross

Doc ID: 307689 Received 21 Sep 2017; Accepted 03 Nov 2017; Posted 03 Nov 2017  View: PDF

Abstract: Capillary optical fibers with hole diameters of several micrometers are important for novel plasmonic applications and medical diagnosis. In order to ensure the optical functionality of these fibers, the diameter of the capillary hole needs to be realized with high accuracy. Here, we introduce a novel and noninvasive methodology to characterize optical fibers and discuss it for the assessment of capillaries. To this end, the diffraction pattern produced by a coherent side-illumination technique of the fiber is analyzed. A numerical parameter retrieval allows us to characterize thecapillary hole diameter with an accuracy of approximately 100 nm for radii in between several hundreds of nanometers and several tens of micrometers.

Broadband rotary joint for high-speed ultrahigh-resolution endoscopic OCT imaging at 800 nm

Hyeon-Cheol Park, Jessica Mavadia-Shukla, Wu Yuan, Milad Alemohammad, and Xingde Li

Doc ID: 307560 Received 20 Sep 2017; Accepted 03 Nov 2017; Posted 03 Nov 2017  View: PDF

Abstract: We report the development of a broadband rotary joint for high-speed ultrahigh-resolution endoscopic optical coherence tomography (OCT) imaging in the 800 nm spectral range. This rotary joint features a pair of achromatic doublets in order to achieve broadband operation for a 3-dB bandwidth over 150 nm. The measured one-way throughput of the rotary joint is greater than 80% while the fluctuation of the double-pass coupling efficiency during 360° rotation is less than +/-5 % at a near video-rate speed of 20 revolutions/second (rps). The rotary joint is used in conjunction with a diffractive-optics-based endoscope and 800 nm spectral domain OCT (SD-OCT) system, and achieved an ultrahigh axial resolution of ~2.4 μm in air. The imaging performance is demonstrated by three-dimensional (3D) circumferential imaging of a mouse colon in vivo.

Two-dimensional tunable orbital angular momentum generation using a vortex fiber

Guobin Ren, Youchao Jiang, ya shen, Yao Xu, Wenxing Jin, Yue Wu, Wei Jian, and Shuisheng Jian

Doc ID: 305813 Received 29 Aug 2017; Accepted 03 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: We demonstrate the two-dimensional tunable orbital angular momentum (OAM) generation in a vortex fiber. The LP₁₁ mode generated by an all fiber fused coupler is coupled into a vortex fiber. Because the vector modes of the LP₁₁ mode group in the vortex fiber are no longer degenerate, the mode status will change between linearly polarized modes (LPMs) and complex OAM modes periodically during propagation. The generated OAM can be tuned smoothly by filtering the mixed mode with different polarization directions or changing the wavelength at a certain polarization direction. The two dimensional turning of OAM from l=-1 to l=+1 is experimentally demonstrated in an all fiber OAM generator.

Nonlinear optical susceptibility of two-dimensional WS₂ measured by Hyper Rayleigh Scattering

Gregory Forcherio, jeremy riporto, Jeremy Dunklin, Yannick Mugnier, ronan Le Dantec, Luigi Bonacina, and Donald Roper

Doc ID: 308235 Received 28 Sep 2017; Accepted 03 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: Hyper Rayleigh Scattering (HRS) was used to measure second-order nonlinear susceptibility, χ^(2), for liquid exfoliated WS2 monolayers. It is the first reported use of concentration-dependent HRS measurements to characterize the bulk-like χ^(2) of a two-dimensional (2D) material. Concentration-dependent HRS signal from a 1064 Nd:YAG laser indicated the first hyperpolarizability for 42 nm WS2 monolayers was 4.90±0.30x10^-25 esu using para-nitroaniline (pNA) as an external reference. The corresponding value of χ_xxx^(2) was calculated to be 460±28 pm V^-1. This was within 46% of independent density functional theory (DFT) predictions. Agreement with theory was improved over related microscopy-based approaches. These results support use of HRS to implement 2D materials into nonlinear frequency mixing applications.

Time reflection and refraction of graphene plasmons at a temporal discontinuity

Galaad Altares Menendez and Bjorn Maes

Doc ID: 308602 Received 05 Oct 2017; Accepted 03 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: A dynamical change of material properties induces a special type of reflection and refraction at a temporal discontinuity. Here we study the interaction of graphene plasmons with single and double temporal discontinuities or shocks, leading to controlled in-plane scattering. We analytically determine the Fresnel-like coefficients for graphene plasmons at these boundaries, and validate our results by rigorous numerical simulations. Temporally controlled doping of two-dimensional materials such as graphene thus leads to a new mechanism for planar and compact plasmonic devices.

Zero-OAM laser printing of chiral nanoneedles

Sergey Syubaev, Alexey Porfirev, Alexey Zhizhchenko, Oleg Vitrik, Sergey Kudryashov, Sergey Fomchenkov, Svetlana Khonina, and Aleksandr Kuchmizhak

Doc ID: 309140 Received 13 Oct 2017; Accepted 03 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: Laser irradiation of various materials including metals, polymers and semiconductors with vortex beams was previously shown to ``twist' transiently molten matter providing the direct easy-to-implement way to obtain chiral surface relief. Specifically for metals, this effect was attributed to transfer of an optical angular momentum (OAM) carried by a vortex beam. In this Letter, we report the formation of twisted metallic nanoneedles on the surface of silver and gold films under their irradiation by a zero-OAM laser beam with a spiral-shaped intensity distribution. Our comparative experiments clearly demonstrate, for the first time, that the formation of the chiral nanoneedles on the noble-metal films is mainly governed by the temperature-gradient induced chiral thermocapillary mass transfer, rather that the OAM-driven rotation of the molten matter.

Schottky Graphene/Silicon Photodetector Based on Hollow-Core Photonic Crystal Fiber

Vahid Ahmadi, Mitra Hosseinifar, and Majid Ebnali-Heidari

Doc ID: 309239 Received 23 Oct 2017; Accepted 03 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: This paper presents a new family of Schottky graphene/silicon photodetector (PD) based on hollow-core photonic crystal fibers (HPCF), working at both optical communication and room temperature. The proposed structure takes the advantage of plasmonic HPCF in slow-light regime and also the absorption mechanism is based on internal photoemission effect (IPE). The main feature of this structure is that the enhanced electric field is strongly localized in the hollow-core of the guided core mode with the surface plasmon modes at the surface metal wires embedded in the photonic crystal (PhC) structure. For the proposed graphene/silicon Schottky PD, numerical simulation predicts responsivity of ~0.39 A/W, and CW sensitivity of -59dBm, that reveals substantial improvements compared to that of typical metal/Si Schottky PDs.

Focusing light through dynamical samples using fast continuous wavefront optimization

Baptiste Blochet, Laurent Bourdieu, and Sylvain Gigan

Doc ID: 307630 Received 20 Sep 2017; Accepted 02 Nov 2017; Posted 03 Nov 2017  View: PDF

Abstract: We describe a fast closed-loop optimization wavefront shaping system able to focus light through dynamic scattering media. A MEMS-based spatial light modulator (SLM), a fast photodetector and FPGA electronics are combined to implement a closed-loop optimization of a wavefront with a single mode optimization rate of 4.1 kHz. The system performances are demonstrated by focusing light through colloidal solutions of TiO2 particles in glycerol with tunable temporal stability.

Cross-correlation photothermal optical coherence tomography with high effective resolution

Peijun Tang, Shaojie Liu, Jun Bo Chen, Zhiling Yuan, Bingkai Xie, Jianhua Zhou, and Zhilie Tang

Doc ID: 307886 Received 25 Sep 2017; Accepted 02 Nov 2017; Posted 03 Nov 2017  View: PDF

Abstract: We developed a cross-correlation photothermal optical coherence tomography (CC-PTOCT) system for photothermal imaging with high lateral and axial resolution. The CC-PTOCT system consists of a phase- sensitive OCT system, a modulated pumping laser and a digital cross-correlator. The pumping laser was used to induced the photothermal effect in the sample, which caused a slight phase modulation of the OCT signals. A spatial phase differentiation method was employed to reduce phase accumulation. The noise brought by the phase differentiation method and the strong background noise were suppressed efficiently by the cross-correlator, which was utilized to extract the photothermal signals from the modulated signals. By combining cross-correlation technique with spatial phase differentiation can improve both lateral and axial resolution of the PT-OCT imaging system. Clear photothermal images of blood capillaries of a mouse ear in vivo was successfully obtained with high lateral and axial resolution. The experimental results demonstrated that this system can enhance the effective transverse resolution, effective depth-resolution and contrast of PT-OCT image effectively, which will aid the ongoing development of the accurate 3D functional imaging.

Experimental Demonstration of a Single Silicon Ring Resonator with an ultra wide FSR and tuning range

ang li and Wim Bogaerts

Doc ID: 307167 Received 20 Sep 2017; Accepted 02 Nov 2017; Posted 03 Nov 2017  View: PDF

Abstract: We present an experimental realization of a pseudo single mode silicon ring resonator with an ultra-wide free spectral range (FSR) and tuning range. The device is a single microring resonator with an tunable reflector integrated inside. The reflector is designed to have zero reflection for only one resonance of the ring, while all other resonance wavelength will suffer strong reflection. Given that reflection inside a ring resonator leads to resonance splitting and degradation of the extinction ratio (ER), we obtain a ring resonator where only a single resonance has a large ER, while all others have a very low ER. The large ER resonance can be continuously tuned using metal heaters to achieve a broad tuning range over 55~nm with 16~mW power injected to the phase shifter.

Effect of pulse asymmetry and nonlinear chirp on the accuracy of ultrafast pulsed laser interferometry

Lei Shao, John Lawall, and Jason Gorman

Doc ID: 307558 Received 22 Sep 2017; Accepted 02 Nov 2017; Posted 03 Nov 2017  View: PDF

Abstract: Ultrafast pulsed laser interferometry (PLI) can measure picometer displacements at sub-nanosecond time scales, such as acoustic waves and vibrations in microstructures. In this letter, the effects of pulse characteristics on the accuracy of PLI are investigated through measurements and modeling. The results show that the effective wavelength of PLI, λeff, varies significantly as a function of overlap between the interfering pulses due to pulse asymmetry and nonlinear chirp. This variation presents a serious limitation on the accuracy of PLI if unaddressed. However, it is shown that a continuous wave laser interferometer can be used to determine λeff with an uncertainty near 0.01 %, making it possible to use PLI for accurate displacement measurements.

Doubly-positive functions in coherent and partially coherent optics

Franco Gori

Doc ID: 308678 Received 10 Oct 2017; Accepted 01 Nov 2017; Posted 03 Nov 2017  View: PDF

Abstract: A function is said to be doubly-positive if it is everywherenon-negative and the same holds true for itsFourier transform. Examples and properties are discussedtogether with procedures to devise classes ofsuch functions. Applications to coherent and partiallycoherent fields are outlined.

Extreme ultraviolet light source at megahertz repetition rate based on high harmonic generation inside a modelocked thin-disk laser oscillator

François Labaye, Maxim Gaponenko, Valentin Wittwer, Andreas Diebold, Clement Paradis, Norbert Modsching, Loïc Merceron, Florian Emaury, Ivan Graumann, Christopher Phillips, Clara Saraceno, Christian Kraenkel, Ursula Keller, and Thomas Sudmeyer

Doc ID: 298279 Received 03 Jul 2017; Accepted 01 Nov 2017; Posted 01 Nov 2017  View: PDF

Abstract: We demonstrate a compact XUV source based on high harmonic generation (HHG) driven directly inside the cavity of a modelocked thin-disk laser (TDL) oscillator. The laser is directly diode-pumped at a power of only 51 W and operates at a wavelength of 1034 nm and 17.4 MHz repetition rate. We drive HHG in a high-pressure xenon gas jet with an intracavity peak intensity of 2.8×10¹³ W/cm² and 320 W of intracavity average power. Despite the high-pressure gas jet, the laser operates at high stability. We detect harmonics up to the 17th order (60.8 nm, 20.4 eV) and estimate a flux of 2.6×10⁸ photons/s for the 11th harmonic (94 nm, 13.2 eV). Due to the power-scalability of the thin-disk concept, this class of compact XUV sources has the potential to become a versatile tool for areas such as attosecond science, XUV spectroscopy, and high-resolution imaging.

Tailoring axial intensity of laser beams with a heart-shaped hole

Yulong Wang, LiJuan Xie, Jia-Sheng Ye, wenfeng sun, Xinke Wang, Shengfei Feng, Peng Han, Qiang kan, and Yan Zhang

Doc ID: 306521 Received 07 Sep 2017; Accepted 01 Nov 2017; Posted 01 Nov 2017  View: PDF

Abstract: We demonstrated a simple heart-shaped hole to tailor the axial intensity of a collimated laser beam. This hole is transformed from a soft-boundary one, which avoids the difficulty in fabricating the soft-boundary mask designed by apodization method, as well as the interference problem caused by the pixel structure of the SLM. When a collimated light passes through this hole, its axial intensity oscillates less than 11% within a certain distance, while the fluctuation after the circular aperture is up to 200%. We compared the propagation of beams after this hole and a circular aperture experimentally and theoretically. The results show that this hole is a useful tool to get the laser beam with uniform axial intensity.

Chip-Scale Optical Vortex Lattice Generator on Silicon Platform

Jian Wang and Jing Du

Doc ID: 306976 Received 14 Sep 2017; Accepted 01 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: An optical vortex (OV) with an isolated field singularity, has been extensively studied in a variety of fields. OV lattice with a network of optical vortices, may find more advanced applications in widespread areas such as optical metrology, optical manipulation, quantum processing, etc. OV lattice generated by traditional approaches relies on a number of bulky diffractive optical elements with large volume and long working distance. Here we present a simple and compact on-chip OV lattice emitter on silicon photonics platforms. The principle relies on three-plane-wave interference. We design, fabricate and demonstrate an on-chip OV lattice emitter consisting of three parallel waveguides with etched tilt gratings. The tilt gratings facilitate flexible light emission in a wide range of directions, enabling the generation of OV lattice above the silicon chip. The demonstrated on-chip OV lattice emitter may open a door to generate, manipulate and detect OV lattice using photonic integrated circuits.

Bit-rate-transparent optical RZ-to-NRZ format conversion based on linear spectral phase filtering of the RZ signal

Reza Maram and Jose Azana

Doc ID: 302837 Received 29 Sep 2017; Accepted 01 Nov 2017; Posted 06 Nov 2017  View: PDF

Abstract: We propose a novel and simple design for all-optical bit-rate-transparent return-to-zero (RZ)-to-non-RZ (NRZ) telecommunication data format conversion based on linear spectral phase filtering of the RZ signal. The proposed concept is numerically analyzed and experimentally validated through successful format conversion of a 640 Gbit/s coherent RZ signal into the equivalent NRZ time-domain data using a simple phase filter realized by a commercial optical waveshaper.

Femtosecond laser pumped plasmonically enhanced NIR random laser based on engineered scatterers

Venkata Siva Gummaluri, Radhika Nair, Sivarama Krishnan, and Vijayan C

Doc ID: 309446 Received 18 Oct 2017; Accepted 31 Oct 2017; Posted 03 Nov 2017  View: PDF

Abstract: In this letter, we report on the design, fabrication and implementation of a novel plasmon-mode-driven low-threshold near infra-red (NIR) random laser (RL) in 850-900 nm range based on plasmonic ZnS@Au core-shell scatterers. Plasmon modes in NIR region are used for nanoscale scatterer engineering of ZnS@Au core-shell particles to enhance scattering, as against pristine ZnS. This plasmonic scattering enhancement coupled with femtosecond laser pumping is shown to cause a three-fold lasing threshold reduction from 325 μJ/cm2 to 100 μJ/cm2 and a mode Q factor enhancement from 200 to 540 for ZnS@Au based RL, as compared to pristine ZnS based RL. Local field enhancement due to plasmonic ZnS@Au scatterers, as evidenced in the Finite-Difference Time-Domain (FDTD) simulation, further adds to this enhancement. This work demonstrates a novel scheme of plasmonic mode coupling in NIR region and femtosecond excitation in a random laser photonic system, overcoming the inherent deficiencies of weak absorption of gain media and poor scattering cross sections of dielectric scatterers for random lasing in NIR spectrum.

Subharmonic anti-phase dynamics in coupled mode-locked semiconductor lasers

Sudarshan Sivaramakrishnan and Herbert Winful

Doc ID: 306808 Received 12 Sep 2017; Accepted 31 Oct 2017; Posted 03 Nov 2017  View: PDF

Abstract: We show that coupled mode-locked semiconductor lasers can operate in a subharmonic regime in which the two lasers pulsate in an anti-phase manner at one-half the fundamental mode-locking frequency of the solitary lasers. In the subharmonic mode each pulse has almost twice the energy carried by the isolated lasers in the fundamental mode-locked regime and is also significantly shorter in duration. Depending on the unsaturated gain and coupling strength the lasers can also exhibit bistability, perfect synchronization, delayed synchronization and three-halves harmonic mode locking. The observed behaviors are robust and persist in the presence of noise.

Cr3+-doped Bi2Ga4O9-Bi2Al4O9 solid-solution phosphors: crystal-field modulation and lifetime-based temperature sensing

Daqin Chen, Xiao Chen, Xiaoyue Li, Hai Guo, Shen Liu, and Xinyue Li

Doc ID: 306350 Received 04 Sep 2017; Accepted 30 Oct 2017; Posted 06 Nov 2017  View: PDF

Abstract: Cr3+-doped Bi2Ga4O9-Bi2Al4O9 solid-solution phosphors were fabricated to explore their possible application in fluorescence-lifetime-based temperature sensing. The present samples exhibited 2E→4A2 R-line emissions associated with 4T2→4A2 phonon sideband emissions of Cr3+ in the wavelength range of 600~850 nm upon the excitation of visible light. Through modifying Ga/Al ratio in the solid-solution hosts, Cr3+ crystal-field was easily tuned from intermediate to strong, being beneficial to modulate energy gap between 2E and 4T2 thermally coupled emitting-states. As a result, linearly temperature-sensitive fluorescence lifetime was achieved in the Cr3+-doped Bi2Ga4O9-Bi2Al4O9 solid-solutions with high Ga/Al ratio, enabling conveniently and accurately determine temperature with high relative sensitivity of 2.13~3.26 %K-1.

Two-Dimensional Microbend Sensor Based on Long Period Fiber Gratings in an isosceles triangle arrangement 3-Core Fiber

song wang, Weigang Zhang, LEI CHEN, Yanxi Zhang, Pengcheng Geng, Yun-Shan Zhang, Tieyi Yan, Lin Yu, Wei Hu, and Yan-Ping Li

Doc ID: 307219 Received 15 Sep 2017; Accepted 30 Oct 2017; Posted 01 Nov 2017  View: PDF

Abstract: To realize the 2D microbend sensor, we designed and fabricated two non-orthogonal long period fiber gratings in our lab made isosceles triangle arranged 3-core optical fiber. To mark two directions without crosstalk, we write two different periods of LPFG in each of the two external cores and central core, which induce a strong asymmetric refractive index arrangement in fiber cross-section. Theoretical and experimental results verify that the resonant wavelength originates from the tunneling between the LP01 core mode in center core and in external core. In the confirmation experiments, the proposed sensor can distinguish multiple bending directions and experiences a maximum sensitivity of 3. 4 nm/m-1 with the bending range of 0–0.588m-1.

On-chip wavelength locking for photonic switches

Akhilesh Khope, Takako Hirokawa, Andrew Netherton, Mitra Saeidi, Yujie Xia, Nicolas Volet, Clint Schow, Roger Helkey, Luke Theogarajan, Adel Saleh, John Bowers, and Rod Alferness

Doc ID: 305974 Received 06 Sep 2017; Accepted 30 Oct 2017; Posted 30 Oct 2017  View: PDF

Abstract: We present an on-chip wavelength reference with a partial drop ring resonator and germanium photo-detector. This approach can be used in ring resonator-based wavelength-selective switches where absolute wavelength alignment is required. We use the temperature dependence of heater resistance as a temperature sensor. Additionally, we discuss locking speed, statistical variation of heater resistances and tuning speed of the switches.

Modified calculation method of relative sensitivity for fluorescence intensity ratio thermometry

Leipeng Li, Yuan Zhou, feng qin, Yangdong Zheng, Hua Zhao, and Zhiguo Zhang

Doc ID: 307331 Received 18 Sep 2017; Accepted 30 Oct 2017; Posted 30 Oct 2017  View: PDF

Abstract: The calculation method of relative sensitivity (Sr) for fluorescence intensity ratio (FIR) thermometry is discussed, taking the 3F3–3H6 and 3H4–3H6 transitions of Tm3+ ion as examples. The value of Sr is calculated using its original definition, and is found to largely deviate from the result obtained using the conventional method that is widely used at present. This deviation is found to stem from the neglect of an offset. A modified expression for Sr is proposed, which shows the true performance of the FIR technology and makes it possible to precisely compare the Sr values obtained using various methods.

Butterfly-inspired micro-concavity array film for color conversion efficiency improvement of quantum-dot-based light emitting diodes

Shudong Yu, Baoshan Zhuang, Junchi Chen, Zongtao li, Longshi Rao, Binhai Yu, and Yong Tang

Doc ID: 307096 Received 25 Sep 2017; Accepted 30 Oct 2017; Posted 06 Nov 2017  View: PDF

Abstract: Inspired by Papilio Blumei butterfly, a microstructured quantum-dot (QD) film with micro-concavity array (MCA) on both surfaces is proposed to enhance color conversion efficiency (CCE) of QD-based white light emitting diodes in this paper. The diameter, aspect ratio and pitch of MCA are optimized in the optical simulations. Both the simulation and experimental results show that the scattering and double reflection effects are the key to the CCE improvement of QD films. The results show that the CCEs are increased from 19.98% to 21.59% and 21.78% (350 mA) for single-side microstructured QD film and double-side microstructured QD film configurations, respectively. Therefore, the proposed microstructured QD film will be a promising alternative to conventional QD layer in illumination and display applications.

Dual-Wavelength Digital Holography with Low-Coherence Light Source based on Quantum Dot Film

Jae-Yong Lee, Sungbin Jeon, JINSANG LIM, Se-Hwan Jang, No-Cheol Park, and Young-Joo Kim

Doc ID: 307998 Received 26 Sep 2017; Accepted 30 Oct 2017; Posted 09 Nov 2017  View: PDF

Abstract: This letter proposes a dual-wavelength, low-coherence digital holography system with a single light source, which utilizes a quantum dot (QD) film as a wavelength converter. By changing the size of QDs, the proposed method yields higher and more uniform illumination easily of any target wavelength, compared with bandpass-filtered light-emitting diodes (LEDs). Fabrication parameters of QD film for better conversion efficiency are discussed. Using this light source with the dual-wavelength reconstruction method extends the efficiency and range of nanoscale three-dimensional height measurements.

Magnetron sputtering deposited WTe2 for ultrafast thulium-doped fiber laser

Jintao Wang, Zike Jiang, hao chen, Jiarong Li, Jinde Yin, Jinzhang Wang, Tingchao He, Peiguang Yan, and Shuangchen Ruan

Doc ID: 307822 Received 25 Sep 2017; Accepted 29 Oct 2017; Posted 06 Nov 2017  View: PDF

Abstract: Ultrafast pulse generation was demonstrated in thulium doped fiber laser mode locked by magnetron sputtering deposited WTe2 with the modulation depth, non-saturable loss and saturable intensity of 31%, 34.3% and 7.6 MW/cm2, respectively. Stable soliton pulses emitting at 1915.5 nm were obtained with pulse duration of 1.25 ps, a 3 dB spectral bandwidth of 3.13 nm, an average output power of 39.9 mW, and signal-to-noise ratio (SNR) of 95 dB. To our knowledge, this is the first demonstration of WTe2-based SA in fiber lasers at 2 μm regime.

Calibrated phase-shifting digital holography based on dual-camera system

Peng Xia, Qinghua Wang, Shien Ri, and Hiroshi Tsuda

Doc ID: 303667 Received 31 Jul 2017; Accepted 28 Oct 2017; Posted 01 Nov 2017  View: PDF

Abstract: A calibrated phase-shifting digital holography system based on the sampling Moiré technique is proposed. Two synchronized cameras are used in this system. One is to record the conventional holograms which include the object information, and the another is to record the interference fringes to analyze phase-shifting errors. An algorithm for improving the quality of the reconstructed images is proposed. In this study, the effectiveness of the proposed system and algorithm is demonstrated in four-step phase-shifting digital holography. The quality of the reconstructed images is greatly improved from both the numerical simulation and experiment.

In situ laser measurement of oxygen concentration and flue gas temperature utilizing chemical reaction kinetics

Jan Viljanen, Tapio Sorvajärvi, and Juha Toivonen

Doc ID: 309552 Received 19 Oct 2017; Accepted 27 Oct 2017; Posted 01 Nov 2017  View: PDF

Abstract: Combustion research requires detailed localized information on the dynamic combustion conditions to improve the accuracy of the simulations and hence improve the performance of the combustion processes. We have applied chemical reaction kinetics of potassium to measure local temperature and O2 concentration in flue gas. Excess of free atomic potassium is created into the measurement volume by photofragmenting precursor molecule such as KCl or KOH that are widely released from solid fuels. The decay of the induced potassium concentration is followed with an absorption measurement using a narrow linewidth diode laser. The temperature and O2 concentration are solved from the decay curve features using equations obtained from calibration measurements in temperature range of 800-1000 °C and in O2 concentrations of 0.1-21 %. Local flue gas temperature and O2 concentration were recorded in real time during devolatilization, char burning and ash cooking phases of combustion in single particle reactor with 5 Hz repetition rate. The method can be further extended to other target species and applications where the chemical dynamics can be disturbed with photofragmentation.

Robust Terahertz Polarizers with High Transmittance at Selected Frequencies through Si Wafer Bonding Technologies

Ting-Yang Yu, Nai-Chen Chi, Hsin-Cheng Tsai, Shiang-Yu Wang, Chih Wei Luo, and Kuan-Neng Chen

Doc ID: 310093 Received 26 Oct 2017; Accepted 27 Oct 2017; Posted 30 Oct 2017  View: PDF

Abstract: Terahertz (THz) polarizers with robust structure and high transmittance are demonstrated using 3D-IC technologies. Cu wire-grid polarizer is sealed and well protected by Si bonded wafers through low temperature eutectic bonding method. Deep reactive-ion etching (DRIE) is used to fabricate the Anti-reflection (AR) layers on outward surfaces of bonded wafers. The extinction ratio (ER) and transmittance of polarizers are between 20dB to 33dB and 13dB to 27dB for 10μm and 20μm pitch wire-grid and 100% at central frequency, depending on frequency and AR layer thickness. The process of polarizer fabrication is simple from mature semiconductor manufacturing techniques that leads to high yield, low cost, and potential for THz applications.

Linear autocorrelation of partially coherent XUV laser pulses: a quantitative analysis

Andréa Le Marec, Olivier Larroche, and Annie Klisnick

Doc ID: 306454 Received 06 Sep 2017; Accepted 26 Oct 2017; Posted 30 Oct 2017  View: PDF

Abstract: A quantitative interpretation method is described for experiments involving the linear autocorrelation of par- tially coherent extreme-ultraviolet (XUV) pulses, gener- ated by either x-ray free-electron lasers or plasma-based XUV lasers. A recently published modeling method for partially coherent pulses is numerically implemented in that specific case. Analytical expressions for the statistical root-mean-square average of the fringe visibility curves are derived. The method yields unambigu- ous informations on both the coherence time and the pulse duration, and should provide a valuable data interpretation tool.

Wide-Field Interferometric Measurement of Nonstationary Complex Coherence Function

Roxana Rezvani Naraghi, Heath Gemar, Mahed Batarseh, Andre Beckus, George Atia, Sergey Sukhov, and Aristide Dogariu

Doc ID: 305765 Received 30 Aug 2017; Accepted 26 Oct 2017; Posted 03 Nov 2017  View: PDF

Abstract: Spatial coherence function (SCF) is a complex function of two spatial coordinates that in general carries more information than the bare intensity distribution. A fast and quantitatively accurate measurement of the SCF is extremely important for a range of applications in optical sensing and imaging. Here, we demonstrate an efficient two-step procedure for measuring the full-field complex coherence function. The measurement relies on an optimized design of a wavefront shearing interferometer that is able to characterize spatially inhomogeneous fields over an extended angular domain. The precision of our coherence measurement is confirmed by the excellent agreement with numerical estimation based on Fresnel calculations. We demonstrate that the sensitivity and the measurement range afforded by our instrument permits to reliably describe the differences in the complex coherence functions that are due to subtle modifications in the shape, position, and orientation of radiation sources.

Ultra-compact waveguide crossing for a mode-division multiplexing optical network

Chunlei Sun, Yu Yu, and Xinliang Zhang

Doc ID: 306748 Received 08 Sep 2017; Accepted 24 Oct 2017; Posted 30 Oct 2017  View: PDF

Abstract: We propose and experimentally demonstrate an ultra-compact multimode waveguide crossing which can process two modes simultaneously. The symmetric Y-junction is introduced to split the high-order mode into fundamental ones, easing the subsequent processing. The footprint of the proposed crossing is as compact as 21 µm × 21 µm. The measured results show insertion loss of ~1.82 dB for TE0 mode and ~0.46 dB for TE1 mode at 1550 nm, as well as crosstalk of < -18 dB from 1510 to 1600 nm.

Intensity Noise Coupling in Soliton Fiber Oscillators

chenchen wan, Thomas Schibli, Peng Li, Carlo Bevilacqua, Axel Ruehl, and Ingmar Hartl

Doc ID: 301071 Received 01 Sep 2017; Accepted 24 Oct 2017; Posted 16 Nov 2017  View: PDF

Abstract: We present an experimental and numerical study on the spectrally resolved pump-to-output intensity noise coupling in soliton fiber oscillators. In our study we observe a strong pump noise coupling to the Kelly sidebands while the coupling to the soliton pulse is damped. This behavior is observed in Erbium-doped as well as Holmium-doped fiber oscillators and confirmed by numerical modeling. It can be seen as a general feature of laser oscillators where soliton pulse formation is dominant. We show that spectral blocking of the Kelly-sidebands outside the laser cavity can improve the intensity noise performance of the laser dramatically

Bismuth-doped All Fiber Mode-locked Laser Operating at 1340nm

Naresh Kumar Thipparapu, Chunyu GUO, Andrey Umnikov, Pranabesh Barua, Austin TARANTA, and Jayanta Sahu

Doc ID: 309157 Received 13 Oct 2017; Accepted 23 Oct 2017; Posted 25 Oct 2017  View: PDF

Abstract: We demonstrate a 1340nm mode-locked Bismuth (Bi)-doped fiber laser without any saturable absorber. The effect of pump power on pulse width is studied and a variation from 1.5 to 3ns is reported. The output of the mode-locked Bi-doped fiber laser (ML-BDFL) is further amplified using a master oscillator power amplifier (MOPA) configuration and a peak power of 1.15W is achieved. Soliton bunching is observed and a true pulse width of 1.2ps is reported from the measured autocorrelation trace. Stable operation of the mode-locked laser is verified from the RF spectrum with a fundamental repetition rate of 6.3MHz, and SNR of 65dB.

Realization of a complementary medium using dielectric photonic crystals

Tao Xu, Anan Fang, Ziyuan Jia, Liyu Ji, and Zhihong Hang

Doc ID: 307924 Received 25 Sep 2017; Accepted 22 Oct 2017; Posted 27 Oct 2017  View: PDF

Abstract: By exploiting the scaling invariance of photonic band diagrams, a complementary photonic crystal slab structure is realized by stacking two uniformly scaled double-zero-index dielectric photonic crystal slabs together. Space cancellation effect in complementary photonic crystals is demonstrated in both numerical simulations and microwave experiments. The refractive index dispersion of double-zero-index dielectric photonic crystal is experimentally measured. Using pure dielectrics, our photonic crystal structure will be an ideal platform to explore various intriguing properties related to complementary medium.

Optical Image Cloning based on Electromagnetic Induced Absorption

Ulices A., Shamaila Manzoor, and Luis de Araujo

Doc ID: 307157 Received 15 Sep 2017; Accepted 18 Oct 2017; Posted 01 Nov 2017  View: PDF

Abstract: We investigate both theoretically and experimentally optical image cloning via Electromagnetic Induced Absorption (EIA). We demonstrate the transfer of small 2D real images imprinted onto a strong coupling beam to a weak probe beam in a rubidium vapor cell. We show that, through EIA, the coupling beam's image is cloned beyond the usual diffraction, with a potential improvement in spatial resolution of the cloned image by a factor of 3 in comparison to that of the original coupling beam. Optical cloning through EIA is based on position selective nonlinear absorption, and it does not rely on spatial modulation of the refractive index.

Asynchronous and synchronous dual-wavelength pulse generation in a passively mode-locked fiber laser with a mode-locker

Guoqing Hu, Yingling Pan, Xin Zhao, Siyao Yin, Meng Zhang, and Zheng Zheng

Doc ID: 306978 Received 18 Sep 2017; Accepted 18 Oct 2017; Posted 03 Nov 2017  View: PDF

Abstract: The evolution from asynchronous to synchronous dual-wavelength pulse generation in a passively mode-locked fiber laser is experimentally investigated by tailoring the intracavity dispersion. Through tuning the intracavity-loss-dependent gain profile and the birefringence-induced filter effect, asynchronous dual-wavelength soliton pulses can be generated until the intracavity anomalous dispersion is reduced to ~8 fs/nm. The transition from asynchronous to synchronous pulse generation is then observed at an elevated pump power in the presence of residual anomalous dispersion, and it is shown that pulses are temporally synchronized at the mode-locker in the cavity. Spectral sidelobes are observed and could be attributed to the four-wave-mixing effect between dual–wavelength pulses at the carbon nanotube mode-locker. These results could provide further insight into the design and realization of such dual-wavelength ultrafast lasers for different applications such as dual-comb metrology as well as better understanding of the inter-pulse interactions in such dual-comb lasers.

High quality factor double Fabry-Perot plasmonic nanoresonator

Baptiste FIX, Julien Jaeck, Patrick Bouchon, sébastien héron, benjamin vest, and Riad Haidar

Doc ID: 308258 Received 29 Sep 2017; Accepted 17 Oct 2017; Posted 27 Oct 2017  View: PDF

Abstract: Fabry-Perot like resonances have been widely describedin nanoantennas. In the original Fabry-Perotresonator, a third mirror can be added, resulting in amultimirror interferometer. However, in the case ofcombination of nanoantennas, it has been reported thateach cavity behaves independently. Here, we evidencethe interferences between two FP absorbing nanoantennasthrough a common mirror, which has a strongimpact on the optical behavior. While the resonancewavelength is only slightly shifted, the level of absorptionreaches nearly 100 %. Moreover, the quality factorincreases up to factor 7 and can be chosen by geometricdesign over a range from 11 to 75. We demonstratethanks to a simple analytical model that this couplingcan be ascribed to a double FP cavity resonance, withthe unique feature that each cavity is separately coupledto the outer medium.

Three-Dimensional Patterned Graphene Oxide-Quantum Dot Microstructures via Two-Photon Crosslinking

Chun-Yu Lin, Hsin-Yu Chang, Te-Fu Yeh, Hsisheng Teng, and Shean-Jen Chen

Doc ID: 307973 Received 28 Sep 2017; Accepted 16 Oct 2017; Posted 01 Nov 2017  View: PDF

Abstract: The two-photon crosslinking of graphene oxide-quantum dots (GOQDs) adopts rose Bengal as the photoactivator to induce the GOQD assembly process. Based on the Förster resonance energy transfer mechanism with oxygen as the crosslinking medium, three-dimensional patterned GOQD microstructures with near diffraction-limit spatial resolution have been fabricated and analyzed by a multiphoton excited fabrication instrument/microscope.

Position-resolved Raman spectra from a laser-trapped single airborne chemical droplet

aimable kalume, Eric Zhu, Chuji Wang, Joshua Santarpia, and Yongle Pan

Doc ID: 307235 Received 15 Sep 2017; Accepted 16 Oct 2017; Posted 09 Nov 2017  View: PDF

Abstract: It could be very useful to detect and monitor the molecules and molecular reactions located in different positions within a micro-sized particle as they respond to various micro-local environments. In this letter, a particular optical trap using two focusing counter-propagating hollow beams was able to stably trap both absorbing and non-absorbing particles in air for long time observation. A technique that can measure the Raman spectra from different submicron positions of a laser-trapped single airborne particle was developed. Spontaneous and stimulated Raman scattering (SRS) spectra originated from different positions of a diethyl phthalate droplet were recorded, and the strong Raman scattering signals are results of cavity-enhanced effects and the localized strong light illumination.

Analytical registration of vertical image drifts in parallel beam tomographic data

Malte Storm, Felix Beckmann, and Christoph Rau

Doc ID: 304177 Received 09 Aug 2017; Accepted 12 Oct 2017; Posted 12 Oct 2017  View: PDF

Abstract: Reconstructing tomographic images of high resolution, as in X-ray microscopy or transmission electron microscopy, is often limited by the stability of stages or sample drifts, which requires an image alignment prior to reconstruction. Feature--based image registration is routinely used to align images, but this technique relies on strong features in the sample or the application of for example gold tracer particles. In this letter, we present an analytic approach for achieving the vertical registration based on the inherent properties of the data acquired for tomographic reconstruction. It is computationally cheap to implement and can be easily integrated into existing reconstruction pipelines.

An inclined emitting slotted single mode laser with 1.7 degree vertical divergence angle for PIC applications

Yejin Zhang, Yanmei Su, Hongwei Qu, Yu Bi, Jiaoqing Pan, Hongyan Yu, Yang Zhang, Jie Sun, Ming Chong, and xinyan sun

Doc ID: 306547 Received 06 Sep 2017; Accepted 11 Oct 2017; Posted 30 Oct 2017  View: PDF

Abstract: In this letter, a new type of single mode slotted laser used for on-chip light source in photonic integrated circuits is proposed. An inclined light beam with a low vertical divergence angle can be directly coupled into the surface grating of the silicon to form an integrated light source. Experimentally, an III-V laser with a 54.6 degree inclined angle and a vertical divergence angle of 1.7 degree is achieved by introducing a kind of specially distributed micro-structure. The side mode suppression ratio is better than 45 dB and the continuous wave output power reaches 6.5 mW at room temperature. We report the inclined emitting micro-structured single mode laser with a low divergence angle for the first time.

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