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Accepted papers to appear in an upcoming issue

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Quantum beam splitter for orbital angular momentum of light: quantum correlation by four-wave mixing operated in a nonamplifying regime

Zhongzhong Qin, Wei Liu, Rong Ma, Li Zeng, and Xiaolong Su

Doc ID: 359168 Received 30 Jan 2019; Accepted 18 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: Nondegenerate four-wave mixing (FWM) processbased on a double-Λ scheme in hot alkali metal vapor isa versatile tool in quantum state engineering, quantumimaging, and quantum precision measurements. In thisLetter, we investigate the generation of quantum correlatedtwin beams which carry nonzero orbital angularmomentums (OAMs) based on the FWM process in hotcesium vapor. The amplified probe beam and the newlygenerated conjugate beam in theFWMprocess have thesame and opposite topological charge as the seed beam,respectively. We also explore the FWM process operatedin a nonamplifying regime where quantum correlatedtwin beams carrying OAMs can still be generated.In this regime, the FWM process plays the role of quantumbeam splitter for the OAMof light, that is, a devicethat can split a coherent light beam carrying OAM intoquantum-correlated twin beams carrying OAMs. Moregenerally, our setup can be used as a quantum beamsplitter of images.

Mode coupling in a terahertz multi-mode whispering-gallery mode resonator

liao chen, Shixing Yuan, Ziwei Wang, Ruolan Wang, Xiaojun Wu, and Xinliang Zhang

Doc ID: 359704 Received 18 Feb 2019; Accepted 18 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: We investigate mode coupling effects of terahertz whispering-gallery modes (WGMs) in a multi-mode resonator using an extended transfer matrix method. Coupling effects between two WGMs are successfully observed on a well-designed high Q terahertz Teflon ring resonator which supports low order WGMs. The extended transmission matrix method is adopted to model, analyze and reproduce terahertz single-band resonance and asymmetric dual-band resonances caused by coupling effects. Moreover, the terahertz splitting effect based on coupling of two modes in a multi-mode resonator is theoretically illustrated. This detailed analysis not only contributes to understanding physical phenomena such as mode splitting but also help in identifying the conditions when designing terahertz devices such as dual band filters.

Novel multipass active stretcher with large chirp for high-flux ultra-intense lasers

hongpeng su, Yujie Peng, Yanyan Li, Xiaoming Lu, Chen Chi, Pengfei Wang, Xinlin Lv, Beijie Shao, and Yuxin Leng

Doc ID: 360467 Received 19 Feb 2019; Accepted 18 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: We demonstrate a novel active multipass stretcher which can deliver pulses with large chirp, adjustable chirped pulse duration and great beam quality for high-flux chirped-pulse amplification system. The stretcher is based on a Martinez-type stretcher and a regenerative amplifier structure, and the laser pulses can be amplified while they are stretched in the cavity. By controlling the roundtrip of the pulses running in the cavity, chirped pulses with more than 10 ns even scaling to 30 ns pulse duration and 20 nm bandwidth can be obtained very easily, which indicates a chirp rate of 0.5 ns/nm at 1053 nm central wavelength. Chirped pulses with several millijoules energy can be delivered with an Nd:glass based intracavity amplifier used to compensate the losses. Benefited by the advantage of the regenerative structure, the output pulses have an excellent beam quality with M2 of 1.1. Finally, the chirped pulses from this novel stretcher are compressed to 1.13 times of Fourier Transform Limit (FTL). With these advantages, this novel multipass active stretcher is significant for ultra-intense laser systems, especially for the high-flux and high-energy 100 petawatt lasers.

Optical signatures of localization-delocalization transition in nitrogen-vacancy centers coupled to photonic crystal cavities

Jiabin You, Wan-Li Yang, gang chen, Zhen-Yu Xu, LIN WU, Ching Eng Png, and Mang Feng

Doc ID: 357178 Received 14 Jan 2019; Accepted 18 Mar 2019; Posted 19 Mar 2019  View: PDF

Abstract: Detecting optical signatures of quantum phase transitions (QPT) in driven-dissipative systems constitutes a new frontier for many-body physics. Here we propose a practical idea to characterize the extensively studied phenomenon of photonic QPT, based on a many-body system composed of nitrogen-vacancy centers embedded individually in photonic crystal cavities, by detecting the critical behaviors of mean photon number, photon fluctuation, photon correlation measurement and emitted spectrum. Our results bridge these experimentally observable quantities to the distinct optical signatures in different quantum phases as good indicators and invaluable tools for studying dynamical properties of dissipative QPT.

Strong interaction of quantum emitters with a WS2layer enhanced by a gold substrate

Vasilios Karanikolas, Ioannis Thanopulos, and Emmanuel Paspalakis

Doc ID: 358537 Received 23 Jan 2019; Accepted 18 Mar 2019; Posted 19 Mar 2019  View: PDF

Abstract: We investigate the spontaneous emission (SE) rate of a two-level quantum emitter (QE) near a WS2 layer, which is placed in a host medium, with a constant dielectric permittivity value. The substrate of the WS2 layer is either a constant dielectric structure, with the same value as the host medium, or Au. We find that the SE rate of the QE near the dielectric/WS2 layer can be enhanced up to 10^4 , compared with its free-space value.When the value of the dielectric permittivity of the host medium of the WS 2 layer is increased, the SE rate diminishes. For a dielectric/WS2 /dielectric structure, we obtain a Rabi splitting in the SE spectrum of the QE up to 75 meV at room temperature. This splitting is more pronounced for a WS2 layer of improved material quality which can be achieved by improved fabrication methods or operating at lower temperatures. When the WS2 layer is placed on top of a Au substrate, the hybrid exciton-surface plasmon polariton modes strongly interact with the QE, inducing coherent energy exchange between the two, as manifested by a pronounced Rabi splitting in the emission spectrum which is increased to 100 meV.

Construction of robust Rydberg controlled-phase gates

Cai-Peng Shen, Jin-Lei Wu, Shi-Lei Su, and Erjun Liang

Doc ID: 358774 Received 28 Jan 2019; Accepted 18 Mar 2019; Posted 19 Mar 2019  View: PDF

Abstract: One scheme is presented to construct the robust multi-qubit arbitrary-phase controlled-phase gate (CPG) in two-level system of Rydberg atoms using the Lewis-Riesenfeld (LR) invariant method. The scheme is not limited by adiabatic condition while preserves the robustness against control parameter variations of adiabatic evolution. Comparing with adiabatic scheme, our scheme does not require very strong Rydberg blockade while the adiabatic case requires it to guarantee adiabatic evolution validity. Taking the construction of two-qubit π CPG as an example, our scheme is more robust against control parametervariations than non-adiabatic scheme and faster than adiabatic scheme.

Transverse-load, strain, temperature, and torsion sensors based on helical photonic crystal fiber

Cailing Fu, Yiping Wang, Shen Liu, Zhiyong Bai, Jian Tang, Laipeng Shao, and Xueya Liu

Doc ID: 359156 Received 01 Feb 2019; Accepted 17 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: We demonstrated a fabrication method of a helical photonic crystal fiber (HPCF) and an inflated HPCF (IHPCF) by use of an inflation-assisted hydrogen-oxygen flame heating technique. The transverse-load, strain, temperature and mechanical torsion properties of the HPCF and IHPCF were investigated experimentally to develop high-sensitivity sensors. The experimental results show that the transverse-load sensitivity could be greatly enhanced by means of enlarging the size of the air holes in the IHPCF. That is, the transverse-load sensitivity, i.e. 15.50 nm/(N•mm-1), of the IHPCF is two times higher than that, i.e. 4.45 nm/(N•mm-1), of the HPCF. Moreover, both HPCF and IHPCF exhibit high strain, temperature and torsion sensitivities. Hence, such an HPCF/IHPCF could have great potential sensing applications.

Frequency comb generation through the locking of domain walls in doubly resonant dispersive optical parametric oscillators

Pedro Parra-Rivas, Lendert Gelens, Tobias Hansson, Stefan Wabnitz, and François Leo

Doc ID: 356186 Received 26 Dec 2018; Accepted 16 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: In this letter we theoretically investigate the formation of localized temporal dissipative structures, and their corresponding frequency combs in doubly resonant dispersive optical parametric oscillators. We derive a nonlocal mean field model, and show that domain wall locking allows for the formation of stable coherent optical frequency combs.

Fast computation of absorption spectra for lidar data processing using principal component analysis

Matthew Hayman, Robert Stillwell, and Scott Spuler

Doc ID: 360784 Received 21 Feb 2019; Accepted 16 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: We describe a principal component based technique for approximating absorption and scattering spectra commonly needed for lidar signal processing. Where previously these calculations had been bottlenecks in our lidar signal processing, the described approach has increased our spectrum calculation speed by over two orders of magnitude. This principal component approach also allows analytically calculated temperature and pressure derivatives which is useful for propagating uncertainty and implementation of global optimization algorithms applied to multi-lidar signal processing.

Optical computing optical coherence tomography with conjugate restrained by dispersion

Wenxin Zhang, Xiao Zhang, Chengming Wang, Wenchao Liao, Shengnan Ai, Jui-Cheng Hsieh, Ning Zhang, and Ping Xue

Doc ID: 359889 Received 11 Feb 2019; Accepted 15 Mar 2019; Posted 19 Mar 2019  View: PDF

Abstract: For all imaging techniques such as optical coherence tomography (OCT), fast imaging speed is always of high demand. Optical computing OCT (OC-OCT or OC2T) has achieved ultrahigh speed for real time 3D imaging without post data processing, but its spatial resolution is lowered down due to an imperfect Fourier transformation in the optical computing process. In this letter, we illustrate the theory of OC2T and prove that the dispersion imbalance between reference arm and sample arm may be introduced to improve the resolution. Furthermore, this novel OC2T technique can also restrain the conjugate signal and enable a conjugate restrained OCT imaging without any additional data processing, achieving ~2 times higher resolution than the typical OC2T. At an imaging speed of as high as 5M-A-scans per second, the dispersion imbalance OC2T has strong ability of restraining the conjugate signal with a conjugate signal rejection ratio of 2.6. Direct conjugate restrained OCT imaging is also demonstrated.

Phase noise measurement of optoelectronic oscillator based on photonic-delay line cross correlation method

ZhiQiang Fan, Qi Qiu, Jun Su, Tianhang Zhang, and Yue Lin

Doc ID: 360529 Received 19 Feb 2019; Accepted 15 Mar 2019; Posted 19 Mar 2019  View: PDF

Abstract: Phase noise measurement of a dual-loop optoelectronic oscillator (OEO) based on dual photonic-delay line cross-correlation method is proposed and experimentally demonstrated. The dual-loop OEO and the phase noise measurement system are combined together by sharing the transmitter of the optical link, which makes the structure of the system simpler. In the part of the dual-loop OEO, the ten kilometers-long fiber is shared by the two loops of the OEO utilizing wavelength division multiplexing (WDM) technique. Higher quality factors are obtained simultaneously by the two loops. In the part of the phase noise measurement system, a lower phase noise floor is realized through cross-correlation method. In the experiments, a signal with oscillation frequency of 10.664 GHz and side-mode suppression ratio (SMSR) of 82.4 dB is generated. Its phase noise is evaluated by the proposed system and PN9000C. The measured results of the two systems are in perfect agreement with each other. The phase noise of the signal is measured as -122 dBc/Hz at 10 kHz frequency offset, and the phase noise floor of the 10 μs delay phase noise measurement system is -148 dBc/Hz at 10 kHz offset at 10.6 GHz when the averaging time is 100.

Photonics-based multifunctional system for simultaneous high-resolution radar imaging and fast frequency measurement

Jingzhan Shi, Fangzheng Zhang, Xingwei Ye, Yue Yang, De Ben, and Shilong Pan

Doc ID: 356410 Received 27 Dec 2018; Accepted 15 Mar 2019; Posted 15 Mar 2019  View: PDF

Abstract: A photonics-based multifunctional system is proposed that can simultaneously implement high-resolution radar imaging and fast frequency measurement. In this system, the radar is realized based on photonic frequency-doubling and de-chirp receiving, and the frequency measurement is achieved by a novel microwave frequency-to-time mapping method. In the experimental demonstration, the radar works in Ku band with a bandwidth of 6 GHz (12-18 GHz), through which inverse synthetic aperture radar (ISAR) imaging with a resolution as high as ~2.5 cm × ~2.5 cm is achieved. The frequency measurement module operates in Ka band, which can achieve a measurement frequency range from 28 GHz to 37 GHz, with a measurement resolution of 40 MHz and a refresh rate of 100 kHz.

Ultra-sensitive photoacoustic detection in a high-finesse cavity with Pound-Drever-Hall locking

Zhen Wang, Qiang Wang, Weipeng Zhang, Haoyun Wei, Yan Li, and Wei Ren

Doc ID: 359569 Received 04 Feb 2019; Accepted 15 Mar 2019; Posted 15 Mar 2019  View: PDF

Abstract: We demonstrate an ultra-sensitive photoacoustic sensor using a low laser power (4 mW) and high-finesse (> 9000) optical cavity. The Pound-Drever-Hall (PDH) method is adopted to lock the external cavity diode laser at 1531.58 nm to the Fabry-Pérot cavity. By placing a photoacoustic cell inside the 130-mm long optical cavity, we obtain an enhancement of more than 630 times in laser power for acetylene (C₂H₂) detection. The present PAS sensor achieves a normalized noise equivalent absorption (NNEA) coefficient of 1.1×10-11 cm-1WHz-1/2 that is the unprecedented sensitivity among all the current PAS sensors. Our results demonstrate the feasibility of merging PAS with a high-finesse cavity using PDH locking for ultra-sensitive trace gas detection.

A Fourier-Domain Mode-Locked (FDML) Laser combined with a Master-Oscillator Power Amplifier (MOPA) architecture

Sebastian Karpf and Bahram Jalali

Doc ID: 357219 Received 09 Jan 2019; Accepted 15 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: Originally introduced in 2005 for high speed optical coherence tomography (OCT), the rapidly wavelength swept Fourier Domain Mode Locked (FDML) Laser still to this day enables highest imaging speeds through a very high speed spectral tuning capability. The FDML laser achieves a tuning bandwidth of over 1/10th of its centre wavelength and can sweep this entire bandwidth in less than a microsecond. Interestingly, even though it covers a very broad spectral range, instantaneously it has a narrow spectral linewidth which puts it in a unique space compared to other high-speed broadband laser sources, like e.g. mode-locked lasers or supercontinuum sources. Although it has been applied for non-linear Raman spectroscopy and imaging, a current drawback of this continuous wave (cw) laser is the relatively low instantaneous power of 10-100 mW. Here we report the combination of an FDML laser with a Master Oscillator Power Amplifier (MOPA) architecture to increase the instantaneous power of the FDML for non-linear optical interactions. The output of an FDML laser around 1060 nm is modulated to short pulses using an electro-optic amplitude modulator (EOM) and subsequently amplified using Ytterbium-doped fibre amplifiers (YDFAs). This generates a spectral rainbow of 65 picosecond pulses, where each pulse has a distinct, monochromatic wavelength. The instantaneous power can be adjusted by the YDFAs to reach non-linear optical excitation regimes. This wavelength swept FDML-MOPA laser will have a vast range of applications in e.g. nonlinear optics, spectroscopy, imaging and sensing.

Compressive Raman imaging with spatial frequency modulated illumination

Camille Scotté, Siddharth Sivankutty, Patrick Stockton, Randy Bartels, and Herve Rigneault

Doc ID: 358230 Received 21 Jan 2019; Accepted 14 Mar 2019; Posted 14 Mar 2019  View: PDF

Abstract: We report a line scanning imaging modality of compressive Raman technology with spatial frequency modulated illumination using a single pixel detector. Wedemonstrate the imaging and classification of three different chemical species at line scan rates of 40 Hz.

System design of a reconfigurable null test using a spatial light modulator for freeform metrology

Romita Chaudhuri, Jonathan Papa, and Jannick Rolland

Doc ID: 359498 Received 04 Feb 2019; Accepted 14 Mar 2019; Posted 14 Mar 2019  View: PDF

Abstract: We report the simulation of an adaptive interferometric null test using a high-definition phase-only spatial light modulator (SLM) to measure form and mid spatial frequencies of a freeform mirror with a sag departure of 150 µm from its base sphere. A state-of-the-art commercial SLM is modeled as a reconfigurable phase computer generated hologram (CGH) that generates a nulling phase function with close to an order of magnitude higher amplitude than deformable mirrors. The theoretical uncertainty in form measurement arising from pixelation and phase quantization of the SLM is 50.62 nm RMS. The calibration requirements for hardware implementation are detailed.

Broadband space-time wave packets propagating 70 m

Basanta Bhaduri, Murat Yessenov, Danielle Reyes, Jessica Pena, Monjurul Meem, Shermineh Rostami, Rajesh Menon, Martin Richardson, and Ayman Abouraddy

Doc ID: 360987 Received 05 Mar 2019; Accepted 14 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: The propagation distance of a pulsed beam in free space is ultimately limited by diffraction and space-time coupling. `Space-time' (ST) wave packets are pulsed beams endowed with tight spatio-temporal spectral correlations that render them propagation-invariant. Here we explore the limits of the propagation distance for ST wave packets. Making use of a specially designed phase plate inscribed by gray-scale lithography and having a laser-damage threshold of ~ 0.5 J/cm^2, we synthesize a ST light sheet of width ~ 700 μm and bandwidth ~ 20 nm and confirm a propagation distance of 70 m.

Influence of longitudinal chromatism on vacuum acceleration by intense radially polarized laser beams

Spencer Jolly

Doc ID: 361910 Received 11 Mar 2019; Accepted 13 Mar 2019; Posted 13 Mar 2019  View: PDF

Abstract: We report with single particle simulations that longitudinal chromatism, a commonly occuring spatio-temporal coupling in ultrashort laser pulses, can have a significant influence in the longitudinal acceleration of electrons via high-power, tightly-focused radially polarized laser beams. This effect can be advantageous, and even more-so when combined with small values of temporal chirp. However, the effect can also be highly destructive when the magnitude and sign of the longitudinal chromatism is not ideal, even at very small magnitudes. This motivates the characterization and understanding of the driving laser pulses, and further study of the influence of similar low-order spatial-temporal couplings on such acceleration.

Dual-chirp Fourier domain mode locked optoelectronic oscillator

Ming Li, Tengfei Hao, Jian Tang, Nuan Nuan Shi, Wei Li, and Ninghua Zhu

Doc ID: 361109 Received 26 Feb 2019; Accepted 13 Mar 2019; Posted 14 Mar 2019  View: PDF

Abstract: The optoelectronic oscillators (OEOs) have been widely investigated to generate ultra-pure single frequency microwave signals. Here, we propose and experimentally demonstrate a dual-chirp Fourier domain mode locked (FDML) OEO to generate dual-chip microwave waveforms. In the proposed FDML OEO, a frequency scanning dual-passband microwave photonics filter based on phase-modulation to intensity-modulation (PM-IM) conversion using an optical notch filter and two laser diodes is incorporated into the OEO cavity. Fourier domain mode locking operation is achieved by synchronizing the scanning period of the filter to the cavity round-trip time. Tunable dual-chirp microwave waveforms with a large time-bandwidth product are generated directly from the FDML OEO cavity in the experiment, which can be used in modern radar systems to improve its range-Doppler resolution.

Multi-slice tomography

Esther Tsai, Federica Marone, and Manuel Guizar-Sicairos

Doc ID: 357549 Received 14 Jan 2019; Accepted 13 Mar 2019; Posted 18 Mar 2019  View: PDF

Abstract: Advances in imaging systems and modelling allow for depth information to be retrieved from projections via virtual sectioning of the imaged object. Here we introduce a regridding method that explicitly and directly incorporates this information into a general and non-iterative tomographic reconstruction algorithm. The method is applicable to any imaging scheme that provides depth-resolved projections. Additionally we show, via numerical simulations, that with this method the required number of projections for adequate angular sampling can be reduced.

Angularly tunable bandpass filter: design, fabrication and characterization

Julien Lumeau, Fabien Lemarchand, Thomas Begou, detlef arhilger, and Harro Hagedorn

Doc ID: 359636 Received 05 Feb 2019; Accepted 11 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: We present a thorough study of a bandpass filter for near-IR region, with bandwidth below 20 nm, high transmission, broad rejection band [350-1100] nm. This filter is angularly tunable between 0 and 50° and shows a shift of the central wavelength from 970 nm down to 880 nm without major changes of its bandwidth and spectral shape for unpolarized light. We first provide a description of the design procedure and then carry out an experimental demonstration using plasma enhanced reactive magnetron sputtering. We finally present an accurate characterization of this class of filter using a custom optical system.

3-D Printed Photoreceptor Phantoms for Evaluating Lateral Resolution of Adaptive Optics Imaging Systems

nikita kedia, Zhuolin Liu, ryan sochol, Johnny Tam, Daniel Hammer, and Anant Agrawal

Doc ID: 359001 Received 08 Feb 2019; Accepted 10 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: With adaptive optics (AO), optical coherence tomography (AO-OCT) and scanning laser ophthalmoscopy (AO-SLO) imaging systems can resolve individual photoreceptor cells in living eyes due to enhanced lateral spatial resolution. However, no standard test method currently exists for experimentally quantifying this parameter in ophthalmic AO imagers. Here, we present 3-D printed phantoms which enable measurement of lateral resolution in an anatomically-relevant manner. We used two-photon polymerization to fabricate two phantoms which mimic the mosaic of cone photoreceptor outer segments at multiple retinal eccentricities. With these phantoms, we demonstrated that the resolution of two multimodal AO systems is similar to theoretical predictions, with some intriguing speckle effects.

Generation of spirally accelerating optical beams

Janice Lan, Fangrong HU, and Yixian Qian

Doc ID: 354695 Received 06 Dec 2018; Accepted 10 Mar 2019; Posted 13 Mar 2019  View: PDF

Abstract: We developed a generalized spectral phase superposition approach for generating accelerating optical beams along arbitrary trajectories. Such beams can be customized by predefining an appropriate superimposed phase pattern that consists of multiple sub-phases. We generated a spirally accelerating beam in a three-dimensional space, and developed an algorithm to improve the uniformity of the intensity along the trajectory by introducing phase-shift factors. We also experimentally verified our numerical simulations. The proposed approach breaks the conventional convex trajectory restrictions. These various accelerating beams would pave the way for optically moving particles along a desire trajectory. The generation of such arbitrary accelerating beams is likely to give rise to new applications in flexible optical manipulation, wave front control, and optical transportation and guidance of particles.

Growth and optoelectronic application of CsPbBr3 thin films deposited by pulsed laser deposition

YU HUANG, Lichun Zhang, JIANBU WANG, Baoyu Zhang, LIANJIE XIN, songren niu, Yuan Zhao, Man Xu, xinbo chu, dengying Zhang, chong Qu, and fengzhou Zhao

Doc ID: 360064 Received 13 Feb 2019; Accepted 10 Mar 2019; Posted 14 Mar 2019  View: PDF

Abstract: All inorganic perovskite CsPbBr3 thin films have been prepared on Si (100) substrate by pulse laser deposition (PLD) technique and the morphology, structure, absorbance and photoluminescence properties of CsPbBr3 thin films are investigated. Photodetector based on CsPbBr3/n-Si heterojunction have been fabricated and the performances of the device were characterized. The heterojunction photodetector exhibited diode-like rectifying behavior. Meanwhile, the photocurrent to dark current ratio and the peak responsivity of the heterojunction were approximately 168.5 and 0.6A/W (-5 V, 520 nm), respectively. Furthermore, the CsPbBr3/n-Si heterojunction photodetector exhibited fast response and recovery times. With the good optoelectronic properties, CsPbBr3 thin films prepared by PLD should be widely applicable to high performance photodetector and other optoelectronic devices.

Study of fluid dynamics at the boundary wall of a microchannel by Bloch surface waves

Agostino Occhicone, Alberto Sinibaldi, Frank Sonntag, Peter Munzert, Norbert Danz, and Francesco Michelotti

Doc ID: 352962 Received 04 Dec 2018; Accepted 09 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: Understanding how a fluid flows at the boundaries when it is confined at the micro/nano scale is crucial for a broad range of engineering and biology applications. We propose an experimental technique based on Bloch surface waves sustained by a one-dimensional photonic crystal to evaluate the speed of the contact line, i.e. the triple junction separating three phases, in the low Reynold’s number regime and with a nanometric resolution. Here, we report on the experimental characterization of the translatory motion of the contact line that separates two water solutions with a relatively high refractive index mismatch (7.35×10^-3) and its slipping over a solid surface. The advantages are the relative simplicity and economy of the experimental configuration.

Ultra-high sensitive light-induced thermalelastic spectroscopy sensor with a high Q-factor quartz tuning fork and a multipass cell

Yufei Ma, Ying He, Yao Tong, Yu Xin, and Frank Tittel

Doc ID: 357396 Received 11 Jan 2019; Accepted 09 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: An ultra-high sensitive light-induced thermalelastic spectroscopy (LITES) sensor based on a resonant high Q-factor quartz turning fork (QTF) and a Herriot multipass cell was demonstrated for the first time. The performance of LITES and widely used tunable diode laser absorption spectroscopy (TDLAS) were experimentally investigated and compared at the same conditions. Carbon monoxide (CO) was chosen as the analyte to verify the reported sensors’ performance. With a minimum detection limit (MDL) of 470 ppb for 60 ms integration time and a noise equivalent absorption (NEA) coefficient of 2.0×10-7 cm-1Hz-1/2, and a MDL of 17 ppb with an optimum integration time of 800 s, the reported LITES sensor showed a superior sensing capability compared with a TDLAS sensor and a conventional quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor

Demonstration of a microelectromechanical tunable F-P cavity based on graphene-bonded fiber devices

Fei Xu, Ye Chen, Cheng Li, Jinhui Chen, Zhu Zheng, Tong Sun, and K. Grattan

Doc ID: 359026 Received 29 Jan 2019; Accepted 08 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: Taking advantage of the high thermal conductivity of graphene, this paper demonstrates a microelectromechanical (MEM) tunable Fabry-Perot (F-P) cavity, based on a graphene-bonded fiber device (GFD) which acts as a microheater. By increasing the electric current from 0 mA to 8 mA in the heater, the temperature of the GFD can rise and approach a value of 760 K theoretically. This high temperature will cause a deformation of the fiber, allowing the graphene-bonded fiber end to form a gap adjustable F-P cavity with a cleaved single mode fiber. The gap in the cavity can be reduced by increasing the current applied, leading the transmittance of the cavity to change. In this work, a highly sensitive current sensor and a tunable mode-locked fiber laser are created based on the MEM tunable F-P cavity.

Self-starting mode-locked Cr:ZnS laser using single-walled carbon nanotubes with resonant absorption at 2.4 μm

Daiki Okazaki, Hayato Arai, Anton Anisimov, Esko Kauppinen, shohei chiashi, Shigeo Maruyama, Norihito Saito, and Satoshi Ashihara

Doc ID: 359846 Received 18 Feb 2019; Accepted 08 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: We develop a mode-locked Cr:ZnS polycrystalline laser using single-walled carbon nanotubes (SWCNTs) that have resonant absorption at the wavelength of 2.4 μm. The laser generates ultrashort pulses of 49 fs duration, 2.4 μm center wavelength, and 9.2 THz (176 nm) spectral span at a repetition rate of 76 MHz. We also confirm self-starting of the mode-locked operation. SWCNTs, if appropriately controlled in terms of their diameters, prove useful as ultrafast, saturable absorbers in the mid-infrared region.

Transient scattering effects and electron plasma dynamics during ultrafast laser ablation of water

Javier Hernandez-Rueda and Dries van Oosten

Doc ID: 357531 Received 11 Jan 2019; Accepted 08 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: We study the dynamics of single shot ultrafast laser ablation of a water/gas interface. We model the extremely nonlinear light-water interaction during the first picosecond by simulating the laser pulse propagation while dynamically calculating the spatial distribution of the dielectric function. We make use of a finite difference time domain algorithm to solve Maxwell equations and Rethfeld’s multiple rate equation model to consider the local excitation of a dense electron plasma. We validate our model by comparing the simulated transient reflectivity with experimental results and find excellent agreement.

Optical interleaver based on nested multiple knot microfiber resonators

yating yi, Jibo Yu, Yuxuan Jiang, Elfed Lewis, Gilberto Brambilla, and Pengfei Wang

Doc ID: 358579 Received 30 Jan 2019; Accepted 08 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: A novel design of nested optical fibre based multiple knot resonators is presented. The design consists of three knot resonators, two of which share a significant fraction of their optical path. The relationship between the knots’ diameter ratio and the transmission spectrum is investigated. The output spectrum is theoretically analyzed using transfer matrix analysis and the calculated results exhibit good agreement with experimental results. The free spectral range (FSR) is varied by simply fine-tuning the diameter of the small knot. The periodic spectrum of this optical microfiber based photonic device has a number of applications in the sensing and communications field, e.g. optical interleavers, frequency combs, filters and fiber lasers. This letter demonstrates that the variation of the output spectrum can be implemented simply by changing the knot sizes and coupling coefficients.

Dual-focal waveguide see-through near-eye display with polarization dependent lenses

Chanhyung Yoo, Kiseung Bang, Changwon Jang, Dongyeon Kim, Chang-Kun Lee, Gee Young Sung, Hong-Seok Lee, and Byoungho Lee

Doc ID: 355938 Received 20 Dec 2018; Accepted 08 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: A waveguide near-eye display (NED) with dual-focal plane using a polarization dependent lens device is proposed. The novel optical device is composed of geometric phase holographic lens, a waveplate and a circular polarizer, which is operating as a concave lens or a see-through optical window depending on the polarization state of the input beam. Such property and ultra-thinness of about 1.5 mm can be applied to combiner-eyepiece lens for augmented reality. This optical device attached to the waveguide provides a two depth plane with polarization multiplexing. We have demonstrated that a proof-of-concept system has image planes at infinity and 20 diopters. The devised system can be expected to offer a better immersive experience compared to a NED system with a single-focal plane.

Diffusion-based single-shot holographic tomography

Ryoichi Horisaki, Kazuki Fujii, and Jun Tanida

Doc ID: 357480 Received 11 Jan 2019; Accepted 08 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: Holographic microscopy is a powerful technique for non-invasive label-free biomedical imaging. Most holographic methods utilize reference light and/or multiple measurements to observe both the amplitude and phase of a light wave passing through a specimen. However, such fundamental requirements degrade the spatial resolution due to the use of a reference carrier, cause difficulties for real-time imaging of dynamic biological events, and make the optical setups bulky. Here, we realized reference-free, single-shot holographic tomography by just inserting a diffuser into the optical path in a conventional microscope setup to generate randomly structured illumination. A three-dimensional complex amplitude field was reconstructed from a single scattered intensity image by means of sparsity-constrained multi-slice phase retrieval.

Deep penetration fluorescence imaging through dense yeast cells suspensions using Airy beams

Yael Roichman and Harel Nagar

Doc ID: 358280 Received 21 Jan 2019; Accepted 08 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: We propose a new method to image fluorescent objects through turbid media base on Airy beam scanning.This is achieved by using the non-diffractive nature of Airy beams, namely their ability to maintain their shape while penetrating through a highly scattering medium.We show, that our technique can image fluorescent objects immersed in turbid media with higher resolution and signal to noise than confocal imaging. As proof-of-principle, we demonstrate imaging of 1μm sized fluorescent beads through a dense suspension of yeast cells with an attenuation coefficient of 51 1/cm at a depth of 90μm.Finally, we demonstrate that our technique can also provide the depth of the imaged object without any additional sectioning.

3D deep encoder-decoder network for fluorescence molecular tomography

Lin Guo, Fei Liu, Chuangjian Cai, Guanglei Zhang, and Jie Liu

Doc ID: 358667 Received 28 Jan 2019; Accepted 08 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: Fluorescence molecular tomography (FMT) is a promising and noninvasive in vivo functional imaging modality. However, the quality of FMT reconstruction is limited by the simplified linear model of photon propagation. Here, an end-to-end three-dimensional deep encoder-decoder (3D-En-Decoder) network is proposed to improve the quality of FMT reconstruction. It directly establishes the nonlinear mapping relationship between the inside fluorescent source distribution and the boundary fluorescent signal distribution. Both numerical simulations and phantom experiments were carried out and the results demonstrated that the 3D-En-Decoder network can greatly improve the image quality and reconstruction efficiency compared with the conventional methods. The mean time of reconstructing a 3D image is only about 0.20s.

BAC Activation by Thermal Quenching in Bismuth/Erbium Co-Doped Fiber

Shuen Wei, Yanhua Luo, Desheng Fan, Gui Xiao, Yushi Chu, BOWEN ZHANG, Yuan Tian, MUHAMMAD TALAL, Matthieu Lancry, and Gang-Ding Peng

Doc ID: 358895 Received 28 Jan 2019; Accepted 08 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: We have investigated thermal quenching effect on the bismuth active center (BAC) in a Bi/Er co-doped fiber (BEDF). The effects from varying quenching conditions are studied and discussed. We report, for the first time, a significant BAC activation achieved by thermal quenching. We observed that the peak luminescence at ~ 1405 nm of the BAC associated with silica (BAC-Si) could be enhanced more than 2 times by thermal quenching. The experimental results indicate that thermal quenching could be an effective way for BAC activation of bismuth doped fibers.

Sub-Rayleigh single-pixel imaging via optical fluctuation

Peilong Hong

Doc ID: 359681 Received 06 Feb 2019; Accepted 07 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: Single-pixel imaging (SPI) is a novel lens-free imaging method quite different from the conventional spatially-resolved imaging, yet suffers the Rayleigh resolution limit imposed by the illumination aperture. Here we show that the Rayleigh resolution limit in SPI can be overcome by employing optical fluctuation. With Nth-order autocorrelation of the signal measured by the bucket detector in SPI, the imaging resolution can surpass the Rayleigh resolution limit by a factor of N. This result is important for optical microscopy based on SPI.

Wideband and low-error microwave frequency measurement using degenerate four-wave mixing-based nonlinear interferometer

Ziyi Lin, Zhirong Chen, Bin Zhang, Fan Li, Jianping Li, Xiaojie Guo, and Zhaohui Li

Doc ID: 356208 Received 28 Dec 2018; Accepted 07 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: We report a broadband and low-error photonic instantaneous frequency measurement (IFM) system for microwave signals using a nonlinear interferometer constructed with cascaded degenerate four-wave mixing (FWM) and in-between dispersion to introduce a tunable time delay. The microwave frequency is interpreted through interference of two idlers generated in cascaded FWM stages. This new approach allows parallel implementation of multiple IFMs without overlap of idler wavelengths used for different IFMs, which is crucial to realize wide frequency coverage and high accuracy without compromising system practicality. A large, 40-GHz measurement bandwidth and a low measurement error around 0.4% have been successfully achieved.

Broadband 1310/1550-nm wavelength demultiplexer based on multimode interference coupler with tapered internal photonic crystal for the SOI platform

Luhua Xu, Yun Wang, Deng Mao, Eslam Elfiky, Zhenping Xing, AMAR KUMAR, Md Ghulam Saber, Maxime Jacques, and David Plant

Doc ID: 359740 Received 07 Feb 2019; Accepted 07 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: We design and experimentally demonstrate a broadband 1310/1550-nm wavelength demultiplexer based on multimode interference coupler with tapered internal photonic crystal (PC) structure for the silicon-on-insulator platform. The tapered internal PC structure is engineered to reflect the C-band light while transmit the O-band light. Novel PC nanotapers are introduced for the internal PC structure, which effectively suppress the sidelobe of the photonic bandgap and enable our device operable over the O-band. The device was fabricated using electron beam lithography and its performance has been experimentally characterized. The measured extinction ratios are higher than 15 dB over a 74 nm bandwidth from 1286 nm to 1360 nm at the O-band, and over a 103 nm bandwidth from 1527 nm to 1630 nm that covers the C-band and the L-band.

Interaction of short laser pulses with model contamination microparticles on a high reflector

Kyle Kafka and Stavros Demos

Doc ID: 357243 Received 11 Jan 2019; Accepted 06 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: The response of model contamination particles located on the surface of a multilayer dielectric mirror when exposed to 1053-nm laser pulses of 10-ps or 0.6-ps duration is investigated. Four different particle types were studied: stainless steel, borosilicate glass, polyethylene, and polytetrafluoroethylene, all having an average diameter of about 40 μm. Irradiation with one laser pulse caused particles to eject from the surface with an onset fluence in the range 5× to 100×, depending on the particle type, below the particle-free, laser-induced damage threshold of the mirror. Morphological analysis showed, however, that the ejection process always generated ablation craters and/or secondary contamination, both of which can degrade the performance of the optic during subsequent pulses. Ejection and damage mechanisms are discussed for each particle type.

Directional Scattering Cancellation for an Electrically Large Dielectric Sphere

Carlo Forestiere, Giovanni Miano, Mariano Pascale, and Roberto Tricarico

Doc ID: 350074 Received 12 Nov 2018; Accepted 06 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: We demonstrate the directional scattering cancellation for a dielectric sphere of radius up to ten times the incident wavelength, by coating it with a surface of finite conductivity. Specifically, the problem of determining the values of the surface conductivity that guarantees destructive interference among hundreds of multipolar scattering orders at the prescribed angular direction is reduced to the determination of the zeros of a polynomial, whose coefficients are analytically known.

Angular Random Walk Improvement of Fiber-Optic Gyroscope Using Active Fiber Ring Resonator

Haisheng Zhang, Xingfan Chen, xiaowu shu, and Cheng Liu

Doc ID: 355686 Received 18 Dec 2018; Accepted 06 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: High precision fiber-optic gyroscopes (FOGs) interrogated with broadband light have angular random walk (ARW) limited by the source relative intensity noise (RIN). A passive fiber ring resonator (passive FRR) reduces the RIN and improves the ARW, but the low power transmission results in a low signal-to-noise ratio at the detection. For a great ARW improvement, the fiber ring resonator should have not only a great RIN reduction but also a large power transmission. An erbium-doped fiber amplifier (EDFA) is inserted in the passive resonator to construct an active fiber ring resonator (active FRR). The EDFA compensates for the loss of the resonator and leads to a high finesse and a greater reduction in the RIN. An experiment demonstrated a 17-dB decrease in the RIN, which reduces the standard deviation by 8.5 dB. Adding the active FRR between the Sagnac interferometer and the broadband light, the detected power reaches 150 μW with the FOG at rest and without modulation, which is about one hundred times of the detected power when using a passive FRR. The phase noise is reduced by 6 dB at the proper frequency. The ARW is improved by 4.9 dB from 1.40 to 0.45 mdeg/hour⁰·⁵. The active FRR reduces the RIN and the shot noise simultaneously which leads to a great ARW improvement of the fiber-optic gyroscopes.

Coherent beam combining of pulsed fiber amplifiers by noncolinear sum-frequency generation

Julijanas Zeludevicius, Rokas Rutkauskas, and Kestutis Regelskis

Doc ID: 356619 Received 03 Jan 2019; Accepted 06 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: In this work, we demonstrate coherent beam combining of laser pulses, amplified in 4 separate Yb-doped fiber amplifiers, by using the second-order nonlinear crystal as a combining element. Active phase control was used, and pulses with 240 ps duration were combined in a noncollinear sum-frequency generation configuration. Conversion/combining efficiency up to 49 % was achieved. The maximum pulse energy of 108 µJ and average power of 97 W were achieved in the combined beam at 519 nm.

Mitigation of Speckle Noise in Laser Doppler Vibrometry by Using a Scanning Average Method

Jinghao Zhu, Yanlu Li, and Roel G. Baets

Doc ID: 360888 Received 25 Feb 2019; Accepted 05 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: We present a scanning average (SA) method used in laser Doppler vibrometry (LDV) systems for mitigating the noise induced by dynamic speckles. In this method, the measurement beam is scanned over the target surface within the area of interest at a relatively high frequency. Then an averaging operation (e.g. low-pass filtering) is applied to the acquired photocurrent signals to remove the impacts of the scan. Movement signals recovered from the averaged photocurrents turn out to have lower speckle-induced noise. We report the experimental demonstration of this technique through the use of a silicon-based photonic integrated circuit (PIC).

Continuously wavelength-tunable blueshifting soliton generated in gas-filled photonic crystal fibers

Zhi Yuan Huang, Yifei Chen, Fei Yu, Ding Wang, ruirui zhao, Yu Zhao, Shoufei Gao, Yingying Wang, Pu Wang, Meng Pang, and Yuxin Leng

Doc ID: 356860 Received 04 Jan 2019; Accepted 05 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: We experimentally demonstrate that the wavelength of blueshifting soliton in a length of gas-filled single-ring photonic crystal fiber (SR-PCF) can be continuously tuned over hundreds of nanometers in the visible spectral region. In the experiments this broad wavelength tunability was achieved through adjusting the energy of 800 nm optical pulses launched into the SR-PCF, while a high energy-conversion efficiency was maintained throughout the tuning process. When Ar gas was filled into the SR-PCF, some interference fringes on the pulse spectrum was observed at high pulse-energy levels due to plasma-induced soliton fission. When He gas was filled and the input pulse energy was properly adjusted, blueshifting soliton could be obtained out of the SR-PCF with a conversion efficiency as high as 84%. Moreover, in both Ar- and He-filled SR-PCFs, some spectral spikes were observed at the resonant spectral region of the SR-PCF, which results from phase-matched nonlinear processes. All these experimental results are confirmed by numerical simulations. © 2018 Optical Society of America

Constructing multifunctional wave plates with stereo-metastructure arrays

Sijia Sun, Yajun Gao, Xiang Xiong, Ruwen Peng, and Mu Wang

Doc ID: 359551 Received 04 Feb 2019; Accepted 05 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: Driven by the development of nanophotonics and integrated optics, manipulating polarization of light with metastructures has been extensively studied in recent decades. So far there are still high demand of more efficient ways to control the polarization state of light with extraordinary performance. In this letter we report on constructing multifunctional wave plates with stereo-metastructure arrays (SMAs) by two-photon absorption polymerization. In one frequency range, the SMA can turn the polarization direction of incident linearly polarized (LP) light to its orthogonal direction, acting as a half-wave plate (HWP). In the other frequency range, it converts the LP incident light to circularly polarized (CP) light, acting as a quarter-wave plate (QWP). Such a multifunctional device is expected to possess an energy efficiency as high as 75%. By encoding SMAs with different rotation angles at different spatial areas, we show that SMAs can be applied in display and sensing, where the focal-plane-array (FPA) imaging demonstrates patterned contrast following different structural distribution.

Offset-free mid-infrared frequency comb based on a mode-locked semiconductor laser

Robert Rockmore, Alexandre Laurain, Jerome Moloney, and R. Jason Jones

Doc ID: 355478 Received 10 Jan 2019; Accepted 04 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: We demonstrate a carrier-envelope offset-free frequency comb in the mid-wavelength infrared (MWIR) based on a passively modelocked vertical external cavity surface emitting laser (VECSEL) operating at 1.6 GHz repetition rate. The 290 mW output spanning 3.0-3.5 μm is generated through difference frequency generation (DFG) in periodically poled lithium niobate (PPLN). The VECSEL pulse train is centered at 1030 nm and amplified up to 11~W in a Yb fiber amplifier system. The output is split to generate a second pulse train at 1560 nm through nonlinear broadening in a Si₃N₄ waveguide followed by amplification in Er gain fiber. DFG between the 1030 nm and 1560 nm pulse trains results in a coherent and offset-free MWIR frequency comb, verified with optical heterodyne beat note measurements. Active stabilization of the VECSEL repetition rate provides a fully stabilized high repetition rate frequency comb in the MWIR, uniquely suited for applications in molecular spectroscopy.

Quasi-distributed vibration sensing using OFDR and weak reflectors

Daniel Leandro, Mengshi Zhu, Manuel Lopez-Amo, and Hideaki Murayama

Doc ID: 355797 Received 20 Dec 2018; Accepted 04 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: We proposed a quasi-distributed vibration sensing technique using in-line weak reflectors and optical frequency domain reflectometry. As a result, we achieved 8 kHz measurable vibration frequency with a 15 ~ 20 cm spatial resolution employing a low repetition rate (~ 8 Hz). Moreover, a frequency of 30 kHz was measured for a 1.5 m spatial resolution. The ability of the system to determine the frequency and amplitude of several sections vibrating simultaneously is evaluated for different configurations. Because of the simple arrangement, high detectable frequency and high sensitivity, this approach is expected to be especially well suited for mechanical vibration sensing applications, particularly in medium-sized structures.

Characterization of weak deep UV pulses using cross-phase modulation scans

Jan Reislöhner, Christoph Leithold, and Adrian Pfeiffer

Doc ID: 358464 Received 22 Jan 2019; Accepted 04 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: Temporal pulse characterization methods can often not be applied to UV pulses due to the lack of suitable nonlinear crystals and very low pulse energies. Here, a method is introduced for the characterization of two unknown and independent laser pulses. The applicability is broad, but the method is especially useful for pulses in the deep UV, because pulse energies on the picojoule-scale suffice. The basis is a spectral analysis of the two interfering UV pulses, while one of the pulses is phase shifted by an unknown VIS-IR pulse via cross-phase modulation. The pulse retrieval is analytic and the fidelity can be checked by comparing the complex-valued data trace with the retrieved trace.

The principle of integrated filtering and digitizing based on periodic signal multiplying

Sitong Wang, Guiling Wu, Yiwei Sun, and Jianping Chen

Doc ID: 356451 Received 28 Dec 2018; Accepted 04 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: We propose a generic integrated filtering and digitizing approach which can complete signal filtering and digitizing simultaneously based on periodic signal multiplying. The filtering response can be reconfigured flexibly by adjusting the temporal shape of the local periodic signal and/or the impulse response of photodetection. The principle and features of proposed structure are analyzed, and experimentally verified in electrical domain and photonic domain. The system responses in line with the theoretical and simulation results are experimentally measured.

Optical activity in monolayer black phosphorus due to extrinsic chirality

Jianfa Zhang, Qilin Hong, wei xu, Zhu Hong, Xiaodong Yuan, and Shiqiao Qin

Doc ID: 359460 Received 01 Feb 2019; Accepted 04 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: The phenomenon of optical activity has fundamental importance and widespread applications in polarization optics, analytical chemistry and molecular biology. In the past two decades, there has been lots of research work on designing metamaterials with strong optical activity, which generally employ chiral plasmonic or dielectric nanostructures with resonant responses. In this letter, we show theoretically and numerically that strong optical activity can be obtained in unpatterned monolayer black phosphorus (BP) without using resonant structures. The optical activity can be attributed to the extrinsic chirality from the mutual orientation of the BP film with in-plane anisotropy and the incident light. The obtained circular dichroism in this atomically thick material is comparable to that in previously reported chiral metamaterials and the optical activity is inherently tunable by controlling the Fermi level of monolayer BP.

Tilt-invariant scanned oblique plane illumination microscopy for large-scale volumetric imaging

Manish Kumar and Yevgenia kozorovitskiy

Doc ID: 359476 Received 04 Feb 2019; Accepted 04 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: This Letter presents the first demonstration of multi-tile stitching for large scale 3D imaging in single objective light-sheet microscopy. We show undistorted 3D imaging spanning complete zebrafish larvae, and over 1 mm3 volumes for thick mouse brain sections. We introduce remote galvo scanning for light-sheet creation and develop a processing pipeline for 3D tiling across different axes. With the improved one photon (1p) tilt-invariant scanned oblique plane illumination (SOPi, /sōpī/) microscope presented here, we demonstrate cellular resolution imaging at depths exceeding 330 µm in optically scattering mouse brain samples, and dendritic imaging in more superficial layers.

Ultraviolet polarized light emitting and detecting dual-functioning device based on nonpolar n-ZnO/i-ZnO/p-AlGaN heterojunction

Jiangnan Dai, Jingwen Chen, Xiaohang Li, Jun Zhang, Hanling Long, Hao-chung Kuo, Yunbin He, and Changqing Chen

Doc ID: 356963 Received 09 Jan 2019; Accepted 04 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: We report on demonstration of 386 nm light emission and detection dual-functioning device based on nonpolar a-plane n-ZnO/i-ZnO/p-Al0.1Ga0.9N heterojunction under both forward and reverse bias. The electroluminescence (EL) intensity under reverse bias is significantly stronger than that under forward bias, facilitated by carrier tunneling when the valence band of p-AlGaN aligns with the conduction band of i-ZnO under reverse bias. Also amid reverse bias, the photodetection responsivity is 0.108 A/W, much larger than that of the reported n-ZnO/p-GaN detectors. Optical polarization of the light emission is studied for potential polarization-sensitive device applications. The demonstration of the proposed device provides an important pathway for the multifunctional devices operating in UV spectrum.

Design of chirped-coupling sidewall Bragg gratings for narrow linewidth distributed feedback lasers

Eugenio Di Gaetano and Marc Sorel

Doc ID: 358200 Received 21 Jan 2019; Accepted 04 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: A chirped-coupling sidewall Bragg grating is proposed to mitigate the nonlinear effects that deteriorate the linewidth in DFB lasers operating at high power and high current regime. This novel grating geometry is analyzed and simulated to extract the optimal design parameters in terms of intra-cavity field distribution. Compared to lasers with uniform Bragg gratings, devices fabricated with a chirped-coupling grating are shown to operate in stable single mode operation over a wider current and power range and exhibit linewidth as narrow as 100 kHz.

910-MHz, watt-level, signal-power-enhanced, compact femtosecond optical parametric oscillator based on bidirectional pumping technique

Yixin Chen, Jintao Fan, wenkai yang, Jun Zhao, Yuxi Chu, and Ming-lie Hu

Doc ID: 358432 Received 22 Jan 2019; Accepted 04 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: We propose a high-efficiency and compact 910-MHz femtosecond optical parametric oscillator, which is harmonically pumped by a ~101 MHz Yb doped fiber laser system. The OPO is capable of delivering watt-level, power-enhanced signals across the telecommunication waveband. The signal power enhancement is realized by exploiting the bidirectional pumping technique. A maximum signal power of 1.04 W at 1502 nm is obtained for an input pump power of 3.8 W. Tunable near-infrared signal pulses with a wavelength range between 1350 and 1610 nm are measured, and the pulse durations vary from 193 to 464 fs. This compact and economic design provide a solution for efficient high repetition rate pulse generation over a large wavelength span, which will be beneficial for a variety of practical applications.

High-order harmonic analysis of anisotropic petahertz photocurrents in solids

Alexandr Lanin, Evgeny Stepanov, Alexander Mitrofanov, Dmitry Sidorov-Biryukov, Andrey Fedotov, and Aleksei Zheltikov

Doc ID: 358994 Received 29 Jan 2019; Accepted 04 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: Polarization maps of high-order harmonics are shown to enable a full vectorial characterization of petahertz electron currents generated in a crystalline solid by an ultrashort laser driver. As a powerful resource of this methodology, analysis of energy–momentum dispersion landscapes, defined by the electron band structure, can help identify, as our analysis shows, special directions within the Brillouin zone that can provide a preferable basis for polarization-sensitive high-harmonic mapping of anisotropic petahertz photocurrents in solids.

Quantum nonlocality for entanglement of quasiclassical states

Shi-Biao Zheng, Zhi-Rong Zhong, Jian-Qi Sheng, and li-Hua Lin

Doc ID: 358239 Received 22 Jan 2019; Accepted 03 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: Entanglement of quasiclassical (coherent) states of two harmonic oscillatorsleads to striking quantum effects and is useful for quantum technologies.These effects and applications are closely related to the nonlocalcorrelations inherent in these states, manifested by the violation of Bellinequalities. With previous frameworks, this violation is limited by thesize of the system, which does not approach the maximum even when the amount of entanglement approaches its maximum. Here we propose a new version of Bell correlation operators, with which a nearly maximal violation can be obtained as long as the associated entanglement approximates to the maximum. Consequently, the revealed nonlocaly is significantly stronger than those with previous frameworks for a wide range of the system size. We present a new scheme for realizing the gate necessary for measurement of the nonlocal correlations. In addition to the use in test of quantum nonlocality, this gate is useful for quantum information processing with coherent states.

Ultrafast mid-infrared fiber laser mode-locked usingfrequency-shifted feedback

Matthew Majewski, Robert Woodward, and Stuart Jackson

Doc ID: 354662 Received 06 Dec 2018; Accepted 03 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: We demonstrate ultrashort pulse generation froma fluoride fiber laser co-doped with holmium andpraseodymium. To date the majority of work focusedon short pulse generation from this class of fiber laserhas employed loss modulators in the cavity, both realand artificial. In this work we alternatively employ afrequency shifting element: an acousto-optic modulator(AOM) in the cavity. This results in mode-lockedoutput of sub-5 ps pulses with 10 nJ of energy at acenter wavelength of 2.86 μm, and a pulse repetitionfrequency of 30.1 MHz, equating to a peak power of1.9 kW. Additional experimental investigation of the relationshipbetween frequency shift and cavity roundtrip offer insight into the complex underlying dynamics.As a complementary mode-locking technique toconventional loss modulation, this method of pulseformationmay greatly expand the design flexibility ofpulsed mid-infrared fiber lasers.

A temporally-modulated laser with an alkali vapor amplifier

He Cai, Qiang Yu, Guofei An, Jiao Yang, Rongyi Ji, Xiaoxu Liu, Juhong Han, weihu zhou, and You WANG

Doc ID: 358072 Received 17 Jan 2019; Accepted 03 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: A diode pumped alkali laser (DPAL) has gained rapidly development in the recent years. In this study, we take the advantages of high gain cross-section and low upper-energy lifetime of an alkali laser to propose a novel type of time-domain-modulated alkali vapor amplifier. By using the amplifier, we experimentally demonstrate the power scaling of a modulated seed laser. The study should offer a new methodology to construct a practice high-powered and high modulated laser source for the long-distance Light Detection And Ranging (LIDAR) system in the future.

Fast controllable confocal focus photoacoustic microscopy using a synchronous zoom opto-sono objective

hai ma, zhong cheng, Zhiyang Wang, xiong kedi, and Sihua Yang

Doc ID: 349394 Received 26 Oct 2018; Accepted 02 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: Although variable optical focus lenses have been exploited in photoacoustic microscopy (PAM) to improve imaging performance, an optical and acoustic synchronous zoom lens-based confocal PAM system has not yet been achieved previously to our knowledge. Here, we develop a fast controllable confocal focus PAM (FC-PAM) equipped with a synchronous zoom opto-sono objective to facilitate horizontal slice imaging of specimens with irregular surfaces or multilayered structures at different depths. The integration of an opto-sono objective of an electrowetting-based zoom lens allows for the adjustment of the confocal focal length. Using this objective, the FC-PAM achieved a confocal focus-shifting range of approximately 6 to 43 millimeters with a high transverse resolution, and the confocal focus-shifting time was substantially reduced. Phantom experiments and human skin imaging were performed to demonstrate that the opto-sono objective has great potential for studying living biological tissue and promoting the development of in vivo rapid-noninvasive PAM depth imaging.

An on-chip silicon Mach-Zehnder interferometer sensor for ultrasound detection

Boling Ouyang, Yanlu Li, Marten Kruidhof, Roland Horsten, Koen van Dongen, and Jacob Caro

Doc ID: 358583 Received 11 Feb 2019; Accepted 02 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: We report a highly sensitive integrated photonics Mach-Zehnder interferometer (MZI) for ultrasound detection. With this sensor we achieve considerable extension of the operation range of MZI pressure sensors used sofar (20 kHz maximum), in particular for the first time entering the MHz regime. Compared to polymer and silicon ring-resonator (RR) ultrasound sensors of others and ourselves (refs. [6-9] manuscript), a very important advantage of this sensor is its gradual transmission characteristic, instead of a sharp RR peak. This allows a wide wavelength-operation range, making operation robust. The sensor is fabricated in SOI technology, enabling small size, mass producibility, low cost and electromagnetic immunity. The sensing spiral is on a thin membrane of size 121 µm × 121 µm. Ultrasound excites the membrane’s vibrational mode and induces modulation of the MZI transmission, which characterizes the ultrasound. Our experiments yield the transfer function, sensitivity and lowest measurable ultrasound pressure, each indicating high grade sensor operation. We discuss how the sensor qualities can be tailored and improved, depending on requirements. The combination of its merits make this on-chip MZI ultrasound sensor very promising for various applications, e.g. all-optical photoacoustic imaging. The novelty of these results and the sensor properties qualify for Optics Letters.

Extended depth-of-field all-optical photoacoustic microscopy with dual non-diffracting Bessel beam

Da Xing, Yicheng Hu, Zhongjiang Chen, and Liangzhong Xiang

Doc ID: 358631 Received 24 Jan 2019; Accepted 02 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: The all-optical photoacoustic microscopy (AOPAM) facilitates high-sensitivity, wide-bandwidth, volumetric imaging without coupling mediums. However, the rapid divergence of Gauss beam restricts the stability and depth of field in typical Gauss AOPAM (G-AOPAM). Here, we report an extended depth-of-field all-optical photoacoustic microscopy using dual non-diffracting Bessel beam (B-AOPAM). Benefiting from the designing, B-AOPAM has unique advantages of increasing depth resolving ability and improving photoacoustic detection sensitivity. The proposed scheme showed optimal lateral resolution of 2.4 µm and long depth of focus of 635 µm, which was tenfold larger than that of the G-AOPAM. The scattering phantoms and in vivo animal experiments demonstrated the imaging feasibility and capability of the B-AOPAM, which can provide noncontact, high spatial resolution imaging of non-flat tissue and contribute to future clinical applications.

Femtosecond-laser-written Ho:KGd(WO4)2 waveguide laser at 2.1 μm

Xavier Mateos, Esrom Kifle, Pavel Loiko, Carolina Romero, Javier Vazquez de Aldana, Airan Rodenas, Viktor Zakharov, Andrei Veniaminov, Magdalena Aguilo, Francesc Diaz, Uwe Griebner, and Valentin Petrov

Doc ID: 358471 Received 23 Jan 2019; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: We report on efficient laser operation of the first holmium monoclinic double tungstate waveguide laser fabricated by femtosecond direct laser writing. A depressed-index buried channel waveguide with a 60 μm diameter circular cladding was inscribed in 5 at.% Ho3+:KGd(WO4)2. It was characterized by confocal microscopy, μ-Raman and μ-luminescence spectroscopy indicating well-preserved crystallinity of its core. Pumped by a thulium bulk laser, the holmium waveguide laser generated 212 mW at 2055 nm with a slope efficiency of 67.2%. The waveguide propagation losses were 0.94±0.2 dB/cm.

Temperature bandwidth of second-harmonic-generation in GdCOB crystal

zhengping wang, Xinle Wang, Fapeng Yu, Hongkai Ren, Feifei Chen, Yuxiang Sun, Xian Zhao, and Xin-guang Xu

Doc ID: 359465 Received 01 Feb 2019; Accepted 01 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: The temperature bandwidth of the second harmonic generation (SHG) phase-matching process was investigated for the GdCa₄O(BO₃)₃ (GdCOB) crystal. GdCOB exhibits a much broader temperature bandwidth in comparison with many familiar non-linear optical (NLO) crystals. For a fundamental wave of 1,064 nm, the maximum temperature bandwidth appeared at (θ = 135°, φ = 47.3°), as predicted by the theoretical calculation and demonstrated by the SHG experiments. The GdCOB crystal is a good candidate for NLO frequency conversions under extreme temperatures.

Dependence of the squeezing and anti-squeezing factors of bright squeezed light on the seed beam power and pump beam noise

Yaohui Zheng, Xiaocong Sun, Yajun Wang, Long Tian, Shaoping Shi, and Kunchi Peng

Doc ID: 355552 Received 18 Dec 2018; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: We demonstrate the dependence of the squeezing and anti-squeezing factors on the seed beam power at different pump beam noise. The results indicate that a seed field injected into the optical parametric amplifier (OPA) dramatically degenerates the squeezing factor due to noise coupling between the pump and seed fields, even if both the pump and seed fields reach the shot noise limit. The squeezing and anti-squeezing factors are immunity to the pump beam noise due to no noise coupling when the system operates for the generation of squeezed vacuum states. The squeezing factor degrades gradually as the pump beam intensity noise or seed beam poweris increased. The influence of the two orthogonal quadrature variations is mutually independentof each other.

Femtosecond Raman frequency shifter – pulse compressor

Leonid Losev, Vladimir Pazyuk, and Alexander Konyashchenko

Doc ID: 355730 Received 26 Dec 2018; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: The conversion to the first Stokes component at a wavelength of 1.8 µm of ytterbium laser radiation with a pulse duration of 270 fs by stimulated Raman scattering (SRS) in hydrogen was carried out by using double-pulse pumping scheme. Simultaneously with SRS the process of nonlinear phase modulation of laser and Stokes waves was observed. The spectrally broadened chirped Stokes pulse was compressed to 35 fs in fused silica optical elements at the output of a Raman cell.

Fabrication and characterization of super-polished wedged borosilicate nano-cells.

Tom PEYROT, Christian Beurthe, Sophie Coumar, Marc Roulliay, Karen PERRONET, Pierre Bonnay, Charles Adams, Yvan Sortais, and Antoine Browaeys

Doc ID: 357428 Received 10 Jan 2019; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: We report on the fabrication of an all-glass vapor cell with a thickness varying linearly between (exactly) 0 and $\sim 1$ $\mu$m. The cell is made in Borofloat glass that allows super polish roughness, a full optical bonding assembling and easy filling with alkali vapors. We detail the challenging manufacture steps and present experimental spectra resulting from off-axis fluorescence and transmission spectroscopy of the Cesium D1 line. The very small surface roughness of $1${\AA} rms is promising to investigate the atom-surface interaction or to minimize parasite stray light.

Watt-scale 50-MHz source of single-cycle waveform-stable pulses in the molecular fingerprint region

Thomas Butler, Daniel Gerz, Christina Hofer, Jia Xu, Christian Gaida, Tobias Heuermann, Martin Gebhardt, Lenard Vamos, Hans Schweinberger, Julia Gessner, Thomas Siefke, Martin Heusinger, Uwe Zeitner, Alexander Apolonskiy, Nicholas Karpowicz, Jens Limpert, Ferenc Krausz, and Ioachim Pupeza

Doc ID: 357850 Received 15 Jan 2019; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: We report a coherent mid-infrared (MIR) source with an unprecedented combination of broad spectral coverage (6 to 18 µm), high repetition rate (50 MHz) and high average power (0.5 W). The waveform-stable pulses emerge via intrapulse difference-frequency generation (IPDFG) in a GaSe crystal, driven by a 30-W-average-power train of 32-fs pulses spectrally centered at 2 μm, delivered by a fiber-laser system. Electro-optic sampling (EOS) of the waveform-stable MIR waveforms reveals their single-cycle nature, confirming the excellent phase matching both of IPDFG and of EOS with 2-μm pulses in GaSe. This work establishes 2-μm femtosecond technology as a new, high-power platform for field-resolved, time-domain and frequency-domain precision metrology in the molecular fingerprint region.

All-optical pulse bursts generation from a nonlinear amplifying loop mirror

Auro Perego

Doc ID: 357868 Received 16 Jan 2019; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: A novel method for the generation of bursts of optical pulses is proposed. It is shown analytically that a nonlinear amplifying loop mirror in single pass configuration can transform a low power input pulse with duration of the order of few ns into a burst consisting of few ps duration pulses with individual pulse energy up to tens of nJ. The burst features, number of pulses, their peak power, energy and duration can be tuned and controlled. The proposed pulse bursts generator may be relevant for material processing and in medical applications involving optical ablation.

Hierarchically Structuring and Synchronous Photoreduction of Graphene Oxide Films by Laser Holography for Supercapacitors

Xiu-Yan Fu, Yonglai Zhang, Hao-Bo Jiang, Dong-Dong Han, Yu-Qing Liu, Hong Xia, and Hong-Bo Sun

Doc ID: 346318 Received 27 Sep 2018; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: Herein, we report a simple laser holography technology for hierarchically structuring and synchronous photoreduction of graphene oxides (GO), toward the development of efficient graphene-based electrodes for supercapacitor applications in cost effectively manners. Hierarchical micro-nanostructures including microscale gratings and layered nanoporous structures formed due to laser treatment induced photoreduction and ablation effect. Interestingly, both the morphology and reduction degree of the laser holography reduced GO (LHRGO) shows strong dependence on the laser intensity, providing the feasibility for controlling the micro-nanostructures, chemical composition and the conductivity of the graphene electrodes. Furthermore, the supercapacitors based on LHRGO show higher capacitance values and better electrochemical performance compared to that based on thermal reduced GO (TRGO) of same reduction level. Photoredution and micro-nanostructuring of GO using laser holography may hold great promise for production of effective carbon-based electrodes towards practical applications in energy storage devices.

Reconfigurable optical generation of 9 Nyquist WDM channels with sinc-shaped temporal pulse trains using a single microresonator-based Kerr frequency comb

Fatemeh Alishahi, Ahmad Fallahpour, Amirhossein Mohajerin Ariaei, Yinwen Cao, Arne Kordts, Martin Pfeiffer, Maxim Karpov, Ahmed Almaiman, Peicheng Liao, Kaiheng Zou, Cong Liu, Ari Willner, Moshe Tur, Tobias Kippenberg, and Alan Willner

Doc ID: 357375 Received 11 Jan 2019; Accepted 01 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: Sinc-shaped temporal pulse trains have a spectrally efficient, rectangular Nyquist spectrum. We demonstrate the simultaneous and reconfigurable optical generation of multiple Nyquist-shaped wavelength-division-multiplexed (WDM) channels having temporal sinc-shaped pulse trains as data carriers. The channels are generated through the insertion of coherent lines using cascaded continuous-wave amplitude modulation around the primary lines of a microresonator-based Kerr optical frequency comb. For each of nine Kerr frequency comb lines, we insert sub-groups of uniform and coherent lines to generate 9 WDM channels. The deviations from ideal Nyquist pulses for the 9 channels at repetition rates of 6 GHz and 2 GHz are between 4.2% - 6.1% and 2% - 4.5% respectively. Each WDM channel is modulated with on-off keying (OOK) at 6 Gbit/s. Also, we show the reconfigurability of this method by varying the number of WDM channels, the generated sinc-shaped pulse train repetition rate, duration, and number of zero-crossings.

946-nm Nd:YAG digital-locked laser at 1.1×10^(-16) in 1 s and transfer-locked to a cryogenic silicon cavity

Alexandre Didier, Stepan Ignatovich, Erik Benkler, Maksim Okhapkin, and Tanja Mehlstaeubler

Doc ID: 359609 Received 07 Feb 2019; Accepted 01 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: We present a Nd:YAG ultra-stable laser system operating at 946~nm and demonstrate a fractional frequency instability of 1.1×10^(-16) at 1 s by pre-stabilizing it to a 30 cm-long ULE cavity at room temperature. All key analog components have been replaced by FPGA-based digital electronics. To reach an instability below the 10^(-16) level, we transfer the stability of a 1542 nm laser stabilized to a cryogenic silicon cavity exhibiting a fractional frequency instability of 4×10^(-17) at 1 s to the laser at 946 nm.

Investigation of single- and multi-carrier modulation formats for Kramers-Kronig and SSBI iterative cancellation receivers

Chuanbowen Sun, Di Che, Honglin Ji, and William Shieh

Doc ID: 358829 Received 28 Jan 2019; Accepted 01 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: The Kramers-Kronig (KK) receiver has recently attracted significant attention due to its capability of field recovery with direct detection. Under minimum phase condition, KK receiver may use either single- or multi-carrier modulation formats. In this Letter, we investigate the appropriate modulation formats for both KK and signal-signal beat interference (SSBI) iterative cancellation (IC) receiver. It is shown that, for the KK receiver the single-carrier modulation format is superior to OFDM, because the multicarrier nature of OFDM signals increases the PAPR which causes violation of minimum phase condition. For the IC receiver, SSBI cancellation is more effective when OFDM modulation format is adopted, thus OFDM is the better fit for IC receivers than single carrier.

Single photon detector with a mesoscopic cycling excitation design of dual gain sections and a transport barrier

Lujiang Yan, Mohammad Abu Raihan Miah, Yu-Hsin Liu, and Yuhwa Lo

Doc ID: 356552 Received 03 Jan 2019; Accepted 01 Mar 2019; Posted 05 Mar 2019  View: PDF

Abstract: Conventional semiconductor single photon detectors are Geiger-mode avalanche photodiodes made of high-quality crystalline semiconductors and require external quenching circuits. Here we report a design of single photon detector having dual gain sections to obtain mesoscopic cycling excitation and an amorphous/crystalline heterointerface to form an electron transport barrier that suppresses gain fluctuations. The dual gain sections are comprised of a crystalline silicon n/p junction and a thin layer of amorphous silicon. At 100 MHz, the device shows single photon detection efficiency greater than 11%, self-recovery time of less than 1ns, and an excess noise factor of 1.22 at an average gain around 75,000 under 8.5V bias.

Highly efficient second-harmonic generation of a reflective waveguide-coupled photonic nanocavity

Bong-Shik Song, Kim Joon, and Dongyeon Kang

Doc ID: 347596 Received 09 Oct 2018; Accepted 01 Mar 2019; Posted 06 Mar 2019  View: PDF

Abstract: In order to enhance the second-harmonic generation (SHG) efficiency in a waveguide-coupled photonic nanocavity, we introduce a reflector at the edge of the waveguide and investigate its influence on the input power and SHG efficiency. The SHG efficiency and critical input power of the reflective waveguide-coupled cavity are controlled by the reflection amplitude and phase delay of the reflector. The SHG efficiency at input power considerably lower than the critical power increases up to three orders of magnitude higher than the case without a reflector. Moreover, an SHG efficiency of 100% at the critical input power, which is twice that of the previous result, can be achieved over a wide phase range. These results prove the feasibility and controllability of highly efficient nonlinear optical devices.

Three-wave radial shearing interferometer

Zhongyu Wang, Shuai Wang, ping yang, and Bing Xu

Doc ID: 341748 Received 06 Aug 2018; Accepted 27 Feb 2019; Posted 06 Mar 2019  View: PDF

Abstract: We propose a simple and compact three-wave radial shearing interferometer (TWRSI). This interferometer is constructed only by a Gabor zone plate (GZP) and a CCD. The nominally plane wavefront under test is diffracted into three orders by the GZP, i.e., a parallel beam, a converging spherical beam and a diverging spherical beam, leading to an interference pattern. In the imaging plane, three beams can be considered as the copies of incident beam, compressed beam and the expanded beam, respectively. A CCD detector located in the vicinity of the GZP records this interference pattern. The interference pattern contains three wavefront differences of the overlapping region of three beams. This RSI is very compact, vibration insensitive, suitable for the measurement of continuous and transient wavefront. The experiment validates the proposed method.

Effect on the longitudinal coherence properties of pseudo thermal light source as a function of source size and temporal coherence

Azeem Ahmad, Tanmoy Mahanty, Vishesh Kumar Dubey, Ankit Butola, Balpreet Ahluwalia, and Dalip Mehta

Doc ID: 349994 Received 05 Nov 2018; Accepted 27 Feb 2019; Posted 07 Mar 2019  View: PDF

Abstract: In the present letter, a synthesized pseudo thermal light source having high temporal coherence (TC) and low spatial coherence (SC) properties is used. The longitudinal coherence (LC) properties of the spatially extended monochromatic light source are systematically studied. The pseudo thermal light source is generated from two different monochromatic laser sources: He-Ne (@ 632 nm) and DPSS (@ 532 nm). It was found that the LC length of such light source becomes independent of the parent laser’s TC length for large source size. For the chosen lasers, the LC length become constant to about 30 μm for laser source size of ≥ 3.3 mm. Thus, by appropriately choosing the source size, any monochromatic laser light source depending on the biological window can be utilized to obtain high axial-resolution in optical coherence tomography (OCT) system irrespective of its TC length. The axial resolution of 650 nm was obtained using 1.2 numerical aperture objective lens at 632 nm wavelength. These findings pay the path for widespread penetration of pseudo-thermal light into existing OCT systems with enhanced performance. Pseudo-thermal light source with high TC and low SC properties could be an attractive alternative light source for achieving high axial-resolution without needing dispersion-compensation as compared to the broadband light source.

Photonic spin Hall effect mediated by bianisotropy

Dmitry Zhirihin, Sergey Li, Denis Sokolov, Alexey Slobozhanyuk, Maxim Gorlach, and Alexander Khanikaev

Doc ID: 351555 Received 09 Nov 2018; Accepted 27 Feb 2019; Posted 04 Mar 2019  View: PDF

Abstract: Coupling of electric and magnetic responses of a scatterer known as bianisotropy enables rich physics and unique optical phenomena, including asymmetric absorption or reflection, one-way transparency, and photonic topological phases. Here we demonstrate yet another feature stemming from bianisotropic response, namely, polarization-dependent scattering of light bybianisotropic dielectric meta-atom with broken mirror symmetry, which yields a photonic analogue of spin Hall effect. Based on a simple dipole model, we explain the origin of the effect confirming our conclusions by experimental observation of photonic spin Hall effect both for a single meta-atom and for an array of them.

Polarization diversity phase modulator for measuring frequency-bin entanglement of a biphoton frequency comb in a depolarized channel

Navin Lingaraju, Oscar Sandoval, Poolad Imany, Daniel Leaird, Michael Brodsky, and Andrew Weiner

Doc ID: 357908 Received 16 Jan 2019; Accepted 27 Feb 2019; Posted 28 Feb 2019  View: PDF

Abstract: Phase modulation has emerged as a technique to create and manipulate high-dimensional frequency-bin entanglement. A necessary step to extending this technique to depolarized channels, such as those in a quantum networking environment, is the ability to perform phase modulation independent of photon polarization. This is also necessary to harness hypertanglement in the polarization and frequency degrees of freedom for operations like Bell state discrimination. However, practical phase modulators are generally sensitive to the polarization of light and this makes them unsuited to such applications. We overcome this limitation by implementing a polarization diversity scheme to measure frequency-bin entanglement for arbitrary orientations of co- and cross-polarized time-energy entangled photon pairs.

Measuring fluorescence into a nanofiber by observing field quadrature noise

Alexander Lvovsky, Paul Barclay, Paul Anderson, Shreyas Jalnapurkar, Eugene Moiseev, Pantita Palittapongarnpim, and Andal Narayanan

Doc ID: 359845 Received 08 Feb 2019; Accepted 27 Feb 2019; Posted 28 Feb 2019  View: PDF

Abstract: We perform balanced homodyne detection of the electromagnenic field in a single-mode tapered optical nanofiber surrounded by rubidium atoms in a magneto-optical trap. Resonant fluorescence of atoms into the nanofiber mode manifests itself as increased quantum noise of the field quadratures. The autocorrelation function of the homodyne detector's output photocurrent exhibits exponential fall-off with a decay time constant of $26.3\pm 0.6$ ns, which is consistent with the theoretical expectation under our experimental conditions. To our knowledge, this is the first experiment in which fluorescence into a tapered optical nanofiber has been observed and measured by balanced optical homodyne detection.

Modal analysis using photonic lanterns coupled to arrays of waveguides

Momen Diab and Stefano Minardi

Doc ID: 352715 Received 23 Nov 2018; Accepted 27 Feb 2019; Posted 27 Feb 2019  View: PDF

Abstract: We present a new concept of an integrated optics component capable of measuring the complex amplitudes of modes at the tip of a multimode waveguide. The device uses a photonic lantern to split the optical power carried by an N-modes waveguide among a collection of single-mode waveguides that excite a periodic array of at least N² single-mode evanescently-coupled waveguides. The power detected at each output of the array is a linear combination of the products of the modal amplitudes, a relation that can, under suitable conditions, be inverted allowing the derivation of the amplitudes and relative phases of the modal mixture at the input. The expected performance of the device and its application to the real-time measurement of modal instability in high power fiber lasers is proposed.

SHG (532 nm)-induced spontaneous parametric downconversion noise in 1064 nm-pumped IR upconversion detectors

Lichun Meng, Anuja Padhye, Christian Pedersen, Majid Ebrahim-Zadeh, and Peter John Rodrigo

Doc ID: 355268 Received 20 Dec 2018; Accepted 26 Feb 2019; Posted 27 Feb 2019  View: PDF

Abstract: As a novel technique for infrared detection, frequency upconversion has been successfully deployed in many applications. However, investigations into the noise properties of upconversion detectors (UCDs) have also received considerable attention. In this letter, we present a new noise source - second harmonic generation (SHG)-induced spontaneous parametric downconversion (SPDC) - experimentally and theoretically shown to exist in short-wavelength-pumped UCDs. We investigate the noise properties of two UCDs based on single-pass 1064 nm-pumped periodically poled LiNbO₃ bulk crystals. One UCD is designed to detect signals in the telecom band and the other in the mid-infrared regime. Our experimental demonstration and theoretical analysis reveal the basic properties of this newly discovered UCD noise source, including its dependence on crystal temperature and pump power. Furthermore, the principle behind the generation of this noise source can also be applied to other UCDs, which utilize nonlinear crystals either in waveguide form or with different bulk materials. This study may also aid in developing methods to suppress the newly identified noise in future UCD designs.

Raman amplification of optical beam carrying orbital angular momentum in a multimode step-index fiber

Shankar Pidishety, Sheng Zhu, Yutong Feng, Balaji Srinivasan, and Johan Nilsson

Doc ID: 357745 Received 15 Jan 2019; Accepted 26 Feb 2019; Posted 26 Feb 2019  View: PDF

Abstract: We experimentally demonstrate up to 15 dB of Raman amplification of pulses at 1115 nm with charge l = +2, S = +1 orbital angular momentum mode (OAMM) in a 5 m long fiber with a 25-μm diameter step-index core. The total output reaches 4.5 kW of peak power and 68.5 µJ of energy in ~15 ns pulses at 4 kHz repetition rate. An Yb-doped fiber source pumps the Raman amplifier at 1060 nm with 60-ns pulses. Using a modal decomposition technique based on a spatial light modulator, we measure a mode purity of 83% in the amplified target OAMM of selected polarization. To the best of our knowledge, this is the first time high energy, peak power, gain and purity are achieved in a fiber Raman amplifier for a single OAMM.

Tuning the magneto-optical Kerr effect by the nanograting cross section

Zhixiong Tang, Ruxian Zhu, Leyi Chen, Zhang Cheng, Zhenxing Zong, Shaolong Tang, and Youwei Du

Doc ID: 356958 Received 07 Jan 2019; Accepted 26 Feb 2019; Posted 26 Feb 2019  View: PDF

Abstract: The magneto-optical Kerr effect, especially the Kerr slope, is of great significance to the magneto-optical device. Herein, we developed a method to tune the magneto-optical effect by the nanograting cross section. Both the simulation and experiment confirm that the resonance strength of the plasmon can be modulated by the nanograting cross section, resulting in the large Kerr slope and Kerr rotation. By designing the nanograting cross section, we obtained the Kerr slope of 0.397º/ nm, which is 4 orders of magnitude higher than the reported results. And the Kerr rotation of the magnetic nanograting reaches up to 1.218º, which is 24 times higher than the flat Co film. Such a huge enhancement on the Kerr slope and the Kerr rotation may have profound applications in magneto-optical devices in the future.

Highly efficient phosphorescent organic light-emitting diodes based on single-layer structure

Ping Chen, Asu Li, Ying Gao, Yu Duan, Yi Zhao, and Ren Sheng

Doc ID: 356989 Received 09 Jan 2019; Accepted 26 Feb 2019; Posted 04 Mar 2019  View: PDF

Abstract: We demonstrated highly efficient single-layer organic light-emitting diodes (OLEDs) based on graded-composition architecture. The single-layer OLEDs comprising graded-composition from a mostly hole-transport material at anode to a mostly electron-transport material at cathode. The resulting device with low turn-on voltage of 2.85 V shows maximum power efficiency and current efficiency of 44.8 lm/W and 42.7 cd/A, respectively. It is found that the emission dopant plays an important role to obtain more balanced charge carriers, causing the recombination zone slightly shift to the center of the device. The results of our work suggest that the graded-composition structure represents a path to achieving highly efficient single-layer

Asymmetry and spin-orbit coupling of light scattered from subwavelength particles

Jorge Olmos-Trigo, Cristina Sanz-Fernandez, Sebastian Bergeret, and Juan Saenz

Doc ID: 355680 Received 17 Dec 2018; Accepted 25 Feb 2019; Posted 04 Mar 2019  View: PDF

Abstract: Light scattering and spin-orbit angular momentum coupling phenomena from subwavelength objects, with electric and magnetic dipolar responses, are receiving an increasing interest. Un- der illumination by circularly polarized light, spin-orbit coupling effects have been shown to lead to significant shifts between the measured and actual position of particles. Here we show that the remarkable angular dependence of these “optical mirages” and those of the intensity, degree of circular polarization (DoCP), and spin and orbital angular momentum of scattered photons, are all linked and fully determined by the dimensionless “asymmetry parameter” g, being independent of the specific optical properties of the scatterer. Interestingly, for g different from 0, the maxima of the optical mirage and angular momentum exchange take place at different scattering angles. In addition we show that the g parameter is exactly half of the DoCP at a right-angle scattering. This finding opens the possibility to infer the whole angular properties of the scattered fields

Near Infrared Temporal Compressive Imaging for Video

qun zhou, Jun Ke, and Edmund Lam

Doc ID: 354791 Received 12 Dec 2018; Accepted 25 Feb 2019; Posted 04 Mar 2019  View: PDF

Abstract: Without decreasing spatial resolution, temporal compressive imaging (TCI) can improve the temporal resolution of an imaging sensor and relax the requirement of data readout speed in high-speed imaging. In this paper, we describe a near infrared TCI system that can reconstruct 500fps videos from coded measurement frames sampled at 50fps.

Giant dual-mode graphene-based terahertz modulator enabled by Fabry-Perot assisted multiple reflection

PeiRen Tang, Jiang Li, Sen-Cheng Zhong, Zhao-Hui Zhai, Bing Zhu, Liang-Hui Du, Ze-Ren Li, and Li-Guo Zhu

Doc ID: 358508 Received 30 Jan 2019; Accepted 25 Feb 2019; Posted 04 Mar 2019  View: PDF

Abstract: We report a high-performance terahertz (THz) modulator with dual operation mode. For the pulse operation mode, the proposed THz modulator has the advantage of high modulation depth (MD) and can operate in a broadband frequency range. We have experimentally achieved a MD larger than 90% for the fifth-order pulse THz echo at 0.8 THz and the MD stays larger than 75% in a broadband frequency range larger than 1 THz. While, for the coherent operation mode, the Fabry-Perot (F-P) interference effect has been taken into consideration and a MD larger than 75% at 0.76 THz has also been realized.

Non-Hermitian heterostructure for two-parameters sensing

Jieun Yim, Han Zhao, Bikashkali Midya, and Liang Feng

Doc ID: 360783 Received 21 Feb 2019; Accepted 25 Feb 2019; Posted 26 Feb 2019  View: PDF

Abstract: Non-Hermitian systems at the exceptional point (EP) degeneracy are demonstrated to be highly sensitive to environmental perturbation. Here, we propose and theoretically investigate a novel multilayered heterostructure favoring double EPs for a unique set of material parameters at which forward- and backward-reflection coefficients vanish, respectively. Such an EP heterostructure is shown to scatter off light when system parameters are perturbed away the degeneracies due to the effect of ambient temperature and mechanical stress fluctuations. The proposed structure is conducive to designing optical responses for two mutually independent parameters sensing.

Distributed Acoustic Sensing for 2D and 3D Acoustic Source Localization

Jiajing Liang, Zhaoyong Wang, Bin Lu, Xiao Wang, Luchuan li, qing ye, Ronghui Qu, and Haiwen Cai

Doc ID: 355449 Received 14 Dec 2018; Accepted 25 Feb 2019; Posted 27 Feb 2019  View: PDF

Abstract: Distributed acoustic sensing (DAS) technology based on Rayleigh backscattering is experiencing a rapid development and leading itself into wider applications, because of the unique capability of measuring sound and vibrations at all point along the sensing fiber. However, most implementations of DAS provide the position of detected sources as a function of distance within the one-dimensional (1D) axial space along the sensing fiber. A DAS system with capability of two-dimensional (2D) and three-dimensional (3D) acoustic source localization in air is demonstrated that uses array signal processing to deal with the spatial correlation of the information measured by optical fiber. Preliminary work has demonstrated, 2D acoustic source localization for multi-targets with narrowband signal source of same frequency, and 3D position for a moving narrowband acoustic source. The results establish a new method which opens up new areas of applications of DAS, such as location and identification for static, dynamic and multiple targets in air or water.

Incidence angle calibration for prismless Total Internal Reflection Fluorescence microscopy

Rodolphe Jaffiol, Dalia El Arawi, Cyrille Vezy, and Marcelina Cardoso Dos Santos

Doc ID: 357417 Received 11 Jan 2019; Accepted 25 Feb 2019; Posted 26 Feb 2019  View: PDF

Abstract: We propose a calibration routine useful to evaluate the incident angle in Total Internal Reflection Fluorescence (TIRF) microscopy. This procedure is based on critical angle measurements conducted in the back focal plane (BFP) of the objective. Such BFP imaging can be easily implemented on any TIRF setup, that makes this technique very attractive. Calibration exactitude was demonstrated by comparing the theoretical angular dependence of the electric field intensity |E|² at glass/water interface with experimental observations

Positive- and negative-tone structuring of crystalline silicon by laser-assisted chemical etching

Maxime Chambonneau, Xinya Wang, Xiaoming Yu, Qingfeng LI, Damien Chaudanson, Shuting Lei, and David Grojo

Doc ID: 356162 Received 26 Dec 2018; Accepted 24 Feb 2019; Posted 25 Feb 2019  View: PDF

Abstract: We demonstrate a structuring method for crystalline silicon using nanosecond laser internal irradiation followed by chemical etching. We show a dramatic dependence of the etch rate on the laser writing speed. Enhanced isotropic etch rates of silicon by laser-induced internal damage was recently demonstrated with strong acids but our results add the possibility to obtain also reduced etch rates leading to different topographies. Material analyses indicate the possibility to efficiently produce high aspect ratio channels thanks to laser-induced porosities as well as silicon micro-bumps due to highly stressed regions. This holds promises for fabricating microfluidic, photovoltaic and micro-electromechanical systems.

Quasi-rhombus metasurfaces as multimode interference couplers for controlling the propagation of modes in dielectric-loaded waveguides

Subhash Singh, Chaonan Yao, Mohamed ElKabbash, Jihua Zhang, Chunlei Guo, and Huanyu Lu

Doc ID: 356277 Received 02 Jan 2019; Accepted 21 Feb 2019; Posted 21 Feb 2019  View: PDF

Abstract: Metasurfaces can control the propagation of free space and guided modes by imparting a phase gradient and modifying the mode propagation properties. Here we propose a design to control optical signals in dielectric-loaded waveguide using quasi-rhombus gradient plasmonioc metasurface structure. The metasurface acts as a multimode interference coupler that can focus, route, and split the propagating field in UV-visible spectral range. The ability to gain full control on waveguided mode with minimal footprint can significantly impact miniaturization of optical devices and photonic integrated circuits.

Directly pumped 10 GHz microcomb modules from low-power diode lasers

Myoung-Gyun Suh, Christine Wang, Cort Johnson, and Kerry Vahala

Doc ID: 358599 Received 24 Jan 2019; Accepted 19 Feb 2019; Posted 20 Feb 2019  View: PDF

Abstract: Soliton microcombs offer the prospect of advanced optical metrology and timing systems in compact form factors. In these applications, pumping of microcombs directly from a semiconductor laser without amplification or triggering components is desirable for reduced power operation and to simplify system design. At the same time, low repetition rate microcombs are required in many comb applications for interface to detectors and electronics, but their increased mode volume makes them challenging to pump at low power. Here, 10 GHz repetition rate soliton microcombs are directly pumped by low-power (< 20 mW) diode lasers. High-Q silica microresonators are used for this low power operation and are packaged into fiber-connectorized modules that feature temperature control for improved long-term frequency stability.

Influence of pumping wavelength on laser properties of Fe2+ ions in ZnSe crystal

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

Doc ID: 359648 Received 06 Feb 2019; Accepted 19 Feb 2019; Posted 04 Mar 2019  View: PDF

Abstract: ZnSe:Fe2+ active laser crystal properties at different excitation wavelengths (2.94 and 4.1 µm) were investigated and noticeable variation of the fluorescence spectra shape and their maxima positions as well as changes in decay times were observed. A stepwise shift of the laser oscillation wavelength from 4.7 µm at 2.94 µm pumping to 4.95 µm at 4.1 µm pumping was achieved at room temperature.

Double-pass microwave photonic sensing system based on low-coherence interferometry

Liwei Li, Xiaoke Yi, Suen Xin Chew, SHIJIE SONG, Linh Nguyen, and Robert Minasian

Doc ID: 355600 Received 18 Dec 2018; Accepted 18 Feb 2019; Posted 22 Feb 2019  View: PDF

Abstract: A novel high-performance microwave photonic sensing system employing a reflective double-pass spectrum slicing sensing scheme, based on low coherence interferometry in combination with a dispersive media, is proposed and experimentally demonstrated. The setup is implemented by configuring a double-pass spectrum slicing sensing scheme, which significantly increases the output power level of a low coherent optical source by about 12dB. Moreover, since the light passes through the same optical path twice, the conversion efficiency between the applied optical path difference (OPD) and the dependent RF resonance shift is doubled compared to the conventional approaches. A very high resolution is also able to be realized thanks to the broad bandwidth of the semiconductor optical amplifier (SOA) spectrum. Additionally, this SOA based scheme enables the potential for future realization of a fully integrated sensing system. As an application example, a highly sensitive displacement sensor was investigated, and the experimental results presented a highly linear relationship between the applied OPDs and the RF frequency shifts. The proposed sensing system successfully achieved a high conversion slope of 5.56GHz/mm and a nearly constant resolution of about 124µm using a Gaussian power density spectrum.

Initial observations of the femtosecond timing jitter at the European XFEL

Henry Kirkwood, Romain Letrun, Takanori Tanikawa, Jia Liu, Motoaki Nakatsutsumi, Moritz Emons, Tomasz Jezynski, Guido Palmer, Max Lederer, Richard Bean, Jens Buck, Samuele di dio cafiso, Rita Graceffa, Jan Gruenert, Sebastian Goede, Hauke Hoeppner, Yoonhee Kim, Zuzana Konopkova, Grant Mills, Mikako Makita, Alexander Pelka, Thomas Preston, Marcin Sikorski, Cedric Takem, Klaus Giewekemeyer, Matthieu Chollet, Patrik Vagovic, Henry Chapman, Adrian Mancuso, and tokushi sato

Doc ID: 358067 Received 30 Jan 2019; Accepted 14 Feb 2019; Posted 14 Feb 2019  View: PDF

Abstract: Intense, ultrashort, and high repetition rate x-ray pulses, combined with a femtosecond optical laser, allow pump-probe experiments with fast data acquisition and femtosecond time resolution. However, the relative timing of the x-ray pulses and the optical laser pulses can be controlled only to a level of the intrinsic error of the instrument which, without characterization, limits the time resolution of experiments. This limitation inevitably calls for a precise determination of relative arrival time, which can be used after measurement for sorting and tagging the experimental data to a much finer resolution than it can be controlled to. The observed root-mean-square timing jitter between x-ray and the optical laser at the SPB/SFX instrument at European XFEL was 308 fs. This first measurement of timing jitter at the European XFEL provides an important step in realizing ultrafast experiments at this novel x-ray source. A method for determining the change in complex refractive index of samples is also presented.

LED-Pumped Active Q-switched Nd:YLF Laser

Zhao Tianzhuo, Hong Xiao, Ge Wenqi, Qixiu Zhong, Jiaqi Yu, Jie Li, Li shan, and Zhongwei Fan

Doc ID: 351259 Received 08 Nov 2018; Accepted 13 Feb 2019; Posted 15 Mar 2019  View: PDF

Abstract: Active Q-switching LED-pumped laser is demonstrated by Nd:YLF crystal with an acousto-optic modulation for the first time. LED spectrum-band pump characteristic is grasped to describe the essential difference between LED pump and single-absorption-peak matching of laser-diode pump or no-matching of lamp pump. An effective absorption spectrum concept is first proposed to characterize the absorption features of the gain material with LED-band pumping. According to this new theory, a flat-top beam profile is designed for pumping Nd:YLF crystal with only a 14 W/cm2 peak power, resulting in a 165 μJ output energy at 1047 nm. More importantly, by using the acousto-optic Q-switching technique, this LED-pumped Nd:YLF laser has successfully realized a TEM00 mode output with a pulse energy of 10.6 μJ and a pulse width of 452 ns.

High-Speed Waveguide Integrated Silicon Photodetector on SiN-SOI Platform for Short Reach Datacom

Avijit Chatterjee, Saumitra Saumitra, Sujit Kumar Sikdar, and Shankar Kumar Selvaraja

Doc ID: 357170 Received 09 Jan 2019; Accepted 07 Feb 2019; Posted 11 Feb 2019  View: PDF

Abstract: We present waveguide integrated high-speed Si photodetector integrated with silicon nitride (SiN) waveguide on SOI platform for short reach data communication in 850 nm wavelength band. We demonstrate a waveguide couple Si pin photodetector responsivity of 0.44 A/W at 25 V bias. The frequency response of the photodetector is evaluated by coupling of a femtosecond laser source through SiN grating coupler of the integrated photodetector. We estimate a 3dB bandwidth of 14 GHz at 20 V bias, highest reported bandwidth for a waveguide integrated Si photodetector. We also present detailed optoelectronic DC and AC characterisation of the fabricated devices. The demonstrated integrated photodetector could enable an integrated solution for scaling of short reach data communication and connectivity.

Optical properties of a melt-quenched metal-organic framework glass

Ang Qiao, Haizheng Tao, Michael Carson, Scott Aldrich, Lynn Thirion, Thomas Bennett, John Mauro, and Yuanzheng Yue

Doc ID: 356201 Received 28 Dec 2018; Accepted 04 Feb 2019; Posted 22 Feb 2019  View: PDF

Abstract: Metal-organic framework (MOF) glasses are characterized by the possession of both inorganic and organic components, linked in a continuous network structure by coordination bonds. The optical properties of MOF glasses have not been reported until now. In this work, we prepared a transparent bubble-free bulk MOF glass, namely, ZIF-62 glass (ZnIm2-xbImx), using our newly developed hot-pressing technique and measured its optical properties. ZIF-62 glass has a high transmittance (up to 90%) in the visible and near-infrared wavelength range, which is comparable to that of many oxide glasses. Using the Becke line nD method, we found that ZIF-62 glass exhibits a similar refractive index (1.56) to most inorganic glasses, though a lower Abbe number (~31). These findings indicate that ZIF-62 glass may find uses as a matrix glass for luminescent materials.

Optical AC coupling power stabilization at frequencies close to the gravitational wave detection band

Steffen Kaufer and Benno Willke

Doc ID: 349735 Received 23 Nov 2018; Accepted 23 Dec 2018; Posted 24 Jan 2019  View: PDF

Abstract: Optical AC Coupling has been established as a highlysensitive alternative to multi-photodiode arrays in thedetection of laser power noise. Previous experimentswere limited by the linewidth of the resonators usedin these experiments. This letter describes a dedicatedsetup, which uses an optical resonator with a linewidthof 4 kHz which is one magnitude smaller than in earlierexperiments. To optimize the Optical AC couplinggain the novel approach of using a tunable impedancematching is described. An Optical AC coupling basedpower stabilization feedback control loop is setup andcharacterized at frequencies overlapping with the terrestrialgravitational wave detection band. The performanceof the new experiment is mainly limited byexpected noise sources down to frequencies of about1 kHz and about 7 dB better than its classical equivalentat frequencies between 8 kHz and 60 kHz.

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