2020
2020
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Record 301 of
Title:Sensing Enhancement at an Exceptional Point in a Nonreciprocal Fiber Ring Cavity
Author(s):Wang, Haotian(1); Guo, Jun(1); Zhang, Jianing(1); Zhou, Wei(1); Wang, Yishan(2); Wu, Xiang(3); Shen, Deyuan(3)Source: Journal of Lightwave Technology Volume: 38 Issue: 8 DOI: 10.1109/JLT.2020.2965626 Published: April 15, 2020Abstract:Sensors operating at an exceptional point (EP) are sufficiently sensitive to small perturbations. In this article, we demonstrate that an EP enhances sensing in the frame of a fiber ring cavity. An air gap inserted into a fiber ring cavity couples the clockwise and counterclockwise propagating modes, leading to eigenfrequency splitting. The EP was achieved in a nonreciprocity cavity constructed using an isolator. A fiber displacement sensor was realized by monitoring the splitting strength in the spectrum, which depends on the width of the air gap. The experimental results showed that the sensitivity of the sensor at the EP was sufficiently enhanced as compared to that in the reciprocal cavity. ? 1983-2012 IEEE.Accession Number: 20201608478791 -
Record 302 of
Title:Repetition rate multiplication control of micro-combs assisted by perfect temporal Talbot effect
Author(s):Zhao, Yanjing(1); Chen, Liao(1); Wang, Weiqiang(2,3); Wang, Ruolan(1); Hu, Hao(1); Wang, Xinyu(2,3); Zhang, Chi(1); Zhang, Wenfu(2,3); Zhang, Xinliang(1)Source: APL Photonics Volume: 5 Issue: 4 DOI: 10.1063/1.5139599 Published: April 1, 2020Abstract:Controllable repetition rate multiplication of micro-combs is demonstrated based on the perfect temporal Talbot effect. With third-order-dispersion being eliminated, the repetition rates of micro-combs can be precisely controlled with strong reconfigurability and compatibility. First, we show the fifth multiplication of the repetition rate with unaffected pulse width and shape in both simulation and experiment. By slightly changing fiber lengths, the repetition rate of a micro-comb is precisely increased by 10 times, 15 times, and 20 times, reaching even 980 GHz. The method is verified to be compatible with perfect crystal solitons in repetition rate multiplication. Combined together, larger repetition rates can be obtained. Besides, the perfect temporal Talbot effect can efficiently reduce both timing jitter and amplitude noise of input pulses, demonstrating the stable generation of high-quality pulses with flexible and high repetition rates. Furthermore, our scheme can avoid the trade-off between acquisition speed and temporal resolution in dual-comb synchronous optical sampling, which is quite useful for the ultrafast detection of transient response in unstable samples. This demonstration will lead to the possible realization of an integrated and flexible repetition rate multiplexer for soliton micro-combs and further promote the development of dual-comb applications and future terahertz science. ? 2020 Author(s).Accession Number: 20201608432523 -
Record 303 of
Title:Luminescence modulation behavior upon in-situ electric field of Sm3+ doped KSr2Nb5O15 ferroelectric ceramics
Author(s):Cao, Shuyao(1); Chen, Qian(1); Liu, Junting(1); Wu, Changying(2); Li, Leilei(1); Xu, Jie(1,3); Cheng, Guanghua(2,4); Gao, Feng(1)Source: Materials Letters Volume: 281 Issue: DOI: 10.1016/j.matlet.2020.128613 Published: 15 December 2020Abstract:Sm3+ doped KSr2Nb5O15 (KSN-Sm) ceramics exhibiting the electro-photoluminescent coupling effect were prepared by two-step sintering technology. The microstructures, electrical and luminescent properties were characterized. In addition, the luminescence modulation behavior upon the application of an in-situ electric field was investigated. It was found that the luminescent emission intensity decreased with increasing in-situ dc bias, and a high modulation ratio of approximately 20%@20 kV/cm was achieved. This work demonstrates that KSN-based ferroelectric ceramics with the tetragonal tungsten bronze structure are promising optical materials with good luminescence modulation behavior. ? 2020 Elsevier B.V.Accession Number: 20203709171334 -
Record 304 of
Title:Research on Partial Negative Curvature Terahertz Hollow-core Waveguide
Author(s):Mu, Qi-Yuan(1,2); Zhu, Yuan-Feng(3); Xue, Lu(4); Zhang, Ya-Ni(4,5); Kong, De-Peng(1); He, Zheng-Quan(1); Liu, Hong-Jun(1); Wang, Li-Li(1)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 49 Issue: 9 DOI: 10.3788/gzxb20204909.0923001 Published: September 1, 2020Abstract:A novel partial negative curvature anti-resonance hollow-core terahertz waveguide is proposed. The waveguide cladding consists of two parts, one part is composed of a dielectric circular tube, which provides a part of the negative curvature boundary for the core; the other part is composed of a plurality of rectangular dielectric layers, and multiple dielectric layers for reducing confinement loss. This waveguide structure does not introduce a new cladding node while adding anti-resonant layers, and it is easy to achieve broadband low-loss transmission of terahertz waves. The full vector finite element method is used for the numerical simulation of the waveguide, and the broadband low loss characteristic is investigated. Based on the simulation analysis, the designed waveguide is printed via 3D printing technology, and the transmission characteristics are tested using a terahertz time-domain spectroscopy system. Experimental results show that the transmission loss of this negative curvature anti-resonance terahertz waveguide is less than 10 dB/m in the range of 0.29~0.42 THz, which is in good agreement with the numerical simulation. ? 2020, Science Press. All right reserved.Accession Number: 20203909225080 -
Record 305 of
Title:Spatial Transformer Part-based Siamese Visual Tracking
Author(s):Zhang, Ximing(1); Lei, Hao(1); Ma, Yilong(1); Luo, Shujuan(2); Fan, Xuewu(1)Source: Chinese Control Conference, CCC Volume: 2020-July Issue: DOI: 10.23919/CCC50068.2020.9189662 Published: July 2020Abstract:Local appearance representation of tracking objects plays a key role in robust visual tracking. While, holistic appearance representation mostly dominates the feature extraction model when describing the target appearance in existing DNN-based trackers, leading to high sensitivity to appearance variation, such as rotation, appearance change, and partial occlusion. We introduce a spatial transformer local part detector, which provides more robust local representation for tracking object and combine the existing Siamese networks for visual tracking simultaneously. To this end, we explicit the spatial transformer networks in the local part detector to detect the discriminative region of tracking objects. The local part detector further passes the detection results to the local cropping module, which comes up with the local structure for the region of interest. Differentiable operations can perform end-to-end learning during local structure construction. We implement the tracking procedure by matching the combined local pattern between candidates and templates in Siamese networks. We extensively prove the effectiveness of the proposed method through the ablation studies of the tracking benchmark, including OTB-2015, VOT-2018, and UAV123. ? 2020 Technical Committee on Control Theory, Chinese Association of Automation.Accession Number: 20203909241466 -
Record 306 of
Title:Phase-locked two-color visible frequency comb system based on 1.5-μm all-polarization-maintaining fiber laser
Author(s):Cai, Yajun(1,2); Pan, Ran(1,2); Hu, Xiaohong(1); Feng, Ye(1); Zhang, Wei(1); Zhao, Wei(1,3); Wang, Yishan(1,2,3)Source: Optical Engineering Volume: 59 Issue: 2 DOI: 10.1117/1.OE.59.2.026107 Published: February 1, 2020Abstract:A two-color visible frequency comb system based on a 1.5-μm all-polarization-maintaining (PM) fiber femtosecond laser was developed. This configuration relies on the implementation of three amplifiers, seeded by a single master oscillator. With the repetition rate (fr) of the oscillator locked to a reference frequency of 200 MHz, the output of the first amplifier was used to generate the feedback signal and achieve simultaneous phase lock of the carrier envelop offset frequency (fceo). The remaining two independently configurable amplifiers followed by highly nonlinear fibers and MgO-doped periodically poled lithium niobite crystals were used to produce visible comb lights at 543 and 633 nm (in air), respectively. By referencing to a hydrogen maser, the Allan deviations of fr and fceo at a gate time of 1 s are 438 μHz and 63 mHz, respectively. The spectral bandwidths of the 543- and 633-nm comb lights are 0.157 and 0.174 nm, respectively, and the single-mode powers of these comb lights are higher than 1 μW. The multiple-branch all-PM fiber-based visible frequency comb system exhibiting a narrow spectrum and a high single-mode power will facilitate the development of optical clocks and wavelength standard calibrations. ? 2020 Society of Photo-Optical Instrumentation Engineers (SPIE).Accession Number: 20201108282304 -
Record 307 of
Title:Near-infrared photodetection in graphene/?-In2Se3 heterostructure
Author(s):Shao, Wen(1,2); Xie, Xiaoping(1,2); Zheng, Yunqiang(1); Wang, Wei(1); Li, Tiantian(1,3); Wang, Feifan(3); Wang, Yong(4); Law, Stephanie(4); Gu, Tingyi(3)Source: Optics InfoBase Conference Papers Volume: Issue: DOI: null Published: October 24, 2020Abstract:Photoresponsivity of 1.17 A/W is observed in graphene/molecular beam epitaxy grown ?-state In2Se3 photodetector at 1550 nm light excitation and 0.35 V bias, with smaller than 2 ms response time. ? OSA 2020, ? 2020 The Author(s)Accession Number: 20211110067678 -
Record 308 of
Title:Tunable electromagnetically induced transparency-like spectrum in lithium niobate on insulator platform with narrow linewidth
Author(s):Yu, Wenqi(1,2); Dai, Shuangxing(1,2); Zhao, Yiru(1,2); Zhao, Qinfeng(2,3); Li, Jinye(1,2); Liu, Jianguo(1,2)Source: IEEE Photonics Journal Volume: 12 Issue: 5 DOI: 10.1109/JPHOT.2020.3025626 Published: October 2020Abstract:An all-pass racetrack-resonator-Bragg gratings (APRR-BG) on thin-film lithium niobate on insulator (LNOI) based coupling resonant system is proposed to generate tunable electromagnetically induced transparency (EIT)-like transmission. The structure is a normal all-pass racetrack-resonator with two Bragg gratings inscribed within the straight waveguides, which introduces two different optical pathways in essence, inducing EIT-like spectrum as a result. We investigate the linewidth, and tunability of the EIT-like spectrum, and manufacturing tolerance of the resonant system by utilising the transfer matrix method. The simulation results indicate an extremely narrow linewidth of several picometers, and a high voltage sensitivity of 0.338 GHz/V@1550 nm, which indicates potential for optical filter, optical switching, and sensing of the system. ? This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information see https://creativecommons.org/licenses/by-nc-nd/4.0/Accession Number: 20212010351918 -
Record 309 of
Title:Orientation-selective elliptic optical vortex array
Author(s):Wang, Y.K.(1); Ma, H.X.(1); Zhu, L.H.(1); Tai, Y.P.(2); Li, X.Z.(1,3,4)Source: Applied Physics Letters Volume: 116 Issue: 1 DOI: 10.1063/1.5128040 Published: January 6, 2020Abstract:We propose an orientation-selective elliptic optical vortex array (OS-EOVA). Using multicoordinate (namely, polar, Cartesian, and elliptic) transformations, three kinds of operations applied on optical vortex elements (including location, rotation, and stretching) were executed to obtain the desired orientation in the observed plane. Then, exploiting the reverse design technique, the above-mentioned operations were mapped onto the initial execution plane via Fourier transform. Based on this, 1D and 2D OS-EOVAs were generated experimentally and the existence of optical vortices was verified. Specific OS-EOVAs were designed, possessing antenna array orientation as well as radial and azimuthal orientation. Compared to existing OVAs, the OS-EOVA provides an additional modulated dimension, i.e., orientation. This technique will open up some potential applications, such as complex manipulation of multiparticle systems and fabrication of micromaterials with orientation. ? 2020 Author(s).Accession Number: 20200207999487 -
Record 310 of
Title:Non-interferometric accurate phase imaging via linear-convergence iterative optimization
Author(s):Huang, Jianhui(1,2); Pan, An(3); Jin, Huiliang(1); Meng, Guoxiang(1); Ye, Qian(1)Source: arXiv Volume: Issue: DOI: null Published: May 12, 2020Abstract:This paper reported a general non-interferometric high-accuracy quantitative phase imaging (QPI) method for arbitrary complex-valued objects. Given by a typical 4-f optical configuration as the imaging system, three frames of small-window phase modulation are applied on the object's Fourier spectrum so that redistributed intensity patterns are produced on the image plane, in which the object phase emerges at different degree. Then, an algebraic relationship that connects the object phase with the output intensity is established to provide us with an approximate closed-form phase recovery. Further, an efficient iterative optimization strategy is developed to turn that approximate solution into an accurate one. Due to the linear convergence property of the iteration, a high-accuracy phase recovery is achieved without requiring heavy iterations. The feasibility and accuracy of the proposed method are verified by both numerical simulations and experiments on diverse phase objects. Copyright ? 2020, The Authors. All rights reserved.Accession Number: 20200450858 -
Record 311 of
Title:Laser written 3D 3T spectro-interferometer: Study and optimisation of the laser-written nano-antenna
Author(s):Bonduelle, Myriam(1); Martin, Guillermo(1); Heras Perez, Irene(1); Morand, Alain(2); D'Amico, Ciro(3); Stoian, Razvan(3); Zhang, Guodong(3,4); Cheng, Guanghua(3,4)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11446 Issue: DOI: 10.1117/12.2562179 Published: 2020Abstract:Stationary Wave Integrated Fourier Transform Spectrometers (SWIFTS) are based on the sampling of a stationary wave using nano-sampling centres on the surface of a channel waveguide. Single nanogroove sampling centres above the waveguide surface will radiate the sampled signal with wide angular distribution, which is not compatible with the buried detection area of infrared detectors, resulting in crosstalk between pixels. An implementation of multiple diffraction nano-grooves (antenna) for each sampling position is proposed as an alternative solution to improve directivity towards the detector pixel by narrowing the scattering angle of the extracted light. Its efficiency is demonstrated from both simulated and measured far field radiative patterns exhibiting a promising method to be used for future integrated IR-SWIFTS. The implementation of the antennas will allow for a high resolution spectrometer in Infra-Red (here 1550nm) with no crosstalk problem (ref. [1]). These antennas, combined with the technology used (direct laser writing) will provide a robust, low-cost efficient tool that can be implemented as a 3D-3T spectro-interferometer (multi telescope beam-combiner), useful for astrophysics applications, such as phase closure studies. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Accession Number: 20210309773570 -
Record 312 of
Title:TiO2-based compact TM-pass polarizer at visible wavelengths with ultra-low power loss
Author(s):Zhao, Qinfeng(1,3); Yu, Wenqi(2,3); Zhao, Yiru(2,3); Dai, Shuangxing(2,3); Liu, Jianguo(2)Source: Optics Communications Volume: 475 Issue: DOI: 10.1016/j.optcom.2020.126282 Published: 15 November 2020Abstract:A compact transverse magnetic (TM)-pass/transverse electric (TE)-stop polarizer with ultra-low power loss at visible wavelengths is theoretically proposed on a TiO2-based platform, which is achieved via the surface plasmon polaritons effect in the hybrid plasmonic grating structure. We design the TiO2 waveguide and optimize the structural parameters of the hybrid plasmonic grating using finite element method (FEM) and 3D Finite-Difference-Time-Domain (FDTD) simulation. The proposed polarizer shows a high extinction ratio over 27 dB from the wavelength of 0.54 to 0.57 μm, a low insertion loss of 0.087 dB at 0.552 μm, a compact size of only 2.64 μm and a great fabrication error tolerance. ? 2020 Elsevier B.V.Accession Number: 20203008966008