2022

• Record 361 of
  
  Title:Polarization insensitive achromatic terahertz metalens based on all-dielectric metasurfaces
  
  Author(s):Qin, Chong(1,2); Fan, Wenhui(1,2,3); Wu, Qi(1,2); Jiang, Xiaoqiang(1,2)
  Source: Optics Communications  Volume: 512  Issue:   DOI: 10.1016/j.optcom.2022.128061  Published: June 1, 2022  
  Abstract:Terahertz wave has great potential in wireless communication, biomedical monitoring and spectroscopy. However, the lack of terahertz functional devices hinders the development of terahertz technology. Metasurface is a kind of novel artificial two-dimensional electromagnetic metamaterials, which can efficiently manipulate the electromagnetic wave at sub-wavelength scale and have the advantages of small size and light weight. Therefore, metasurfaces provide an additional modality to realize terahertz functional devices. Terahertz metalens based on metasurfaces is an indispensable functional component, but there is chromatic aberration that will degrade its performance when broadband terahertz wave is incident, so it is very important to eliminate the chromatic aberration of terahertz metalens, especially for terahertz imaging, and so on. In this paper, we elaborate the principle of elimination of chromatic aberration and design a polarization insensitive achromatic metalens working in the frequency range from 0.8 THz to 1.2 THz with numerical aperture of 0.46, three types of meta-atoms with different cross-section shapes are adopted to constitute achromatic metalens. The numerical simulation has also been carried out for the proposed achromatic metalens. The maximum deviation of focal length and average focusing efficiency of the proposed achromatic metalens across the working frequency range is 4.74% and 38.47%, respectively. Meanwhile, the achromatic metalens is polarization insensitive due to the symmetric cross-section shapes of meta-atoms adopted. The polarization insensitive achromatic metalens will pave the way for the practical application of terahertz devices based on metasurfaces. © 2022 Elsevier B.V.
  Accession Number: 20220911739561
• Record 362 of
  
  Title:Deep-Learning-Based Rapid Imaging Through Scattering Media beyond the Memory Effect
  
  Author(s):Zhou, Meiling(1); Bai, Chen(1); Zhang, Yang(1); Li, Runze(1); Peng, Tong(1); Qian, Jia(1); Dan, Dan(1); Min, Junwei(1); Zhou, Yuan(1); Yao, Baoli(1)
  Source: IEEE Photonics Technology Letters  Volume: 34  Issue: 5  DOI: 10.1109/LPT.2022.3153665  Published: March 1, 2022  
  Abstract:By incorporating the ptychography with the shower-curtain effect (PSE), a large field-of-view object hidden behind the scattering media can be reconstructed from multiple diffused patterns. However, the original PSE method is subjected to low speed data acquisition and time-consuming image reconstruction because of the mechanical scanning scheme and the iterative retrieval algorithm. Here, a deep-learning method based on the PSE with improved optical scheme is proposed to accelerate the data acquisition and image reconstruction speed. By replacing the mechanical translation stage with the digital micromirror device (DMD), it facilitates a large number of data collection for training the network. Single-shot pattern and sub-second reconstruction for the well-trained network model make the method appropriate for rapid imaging. Both qualitative presentation and quantitative analysis for binary resolution target and 2D biological slide specimens demonstrate the effectiveness and feasibility of the proposed method, thereby offering a prospective application in tissue imaging. © 1989-2012 IEEE.
  Accession Number: 20220911726507
• Record 363 of
  
  Title:Dual-core negative curvature fiber-based terahertz polarization beam splitter with ultra-low loss and wide bandwidth
  
  Author(s):Hui, Zhan-Qiang(1); Gao, Li-Ming(1); Liu, Rui-Hua(1); Han, Dong-Dong(1); Wang, Wei(2)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 71  Issue: 4  DOI: 10.7498/aps.71.20211650  Published: February 20, 2022  
  Abstract:A novel terahertz polarization beam splitter (PBS) with low loss and large bandwidth based on double core negative curvature fiber is designed. The device takes copolymers of cycloolefin as the substrate, and 12 circular tubes with embedded tubes are evenly distributed along the circumference. The fiber core is divided into two cores through two groups of circumscribed small clad tubes symmetrical up and down. The finite-difference time-domain (FDTD) method is used to analyze its guide mode properties. The effects of various structural parameters on its beam splitting characteristics are investigated in detail, and the extinction ratio (ER), bandwidth and transmission loss of the PBS are analyzed. The simulation results show that when the incident light frequency is 1THz and the beam splitter length is 6.224 cm, the ER of x-polarized light reaches 120.8 dB, the bandwidth with ER above 20 dB is 0.024 THz, the ER of y-polarized light reaches 63.74 dB, the bandwidth with ER above 20 dB is 0.02THz, and the total transmission loss is as low as 0.037 dB/cm. Tolerance analysis shows that the PBS can still maintain good performance under the ±1% deviation of structural parameters. Copyright © 2022 Acta Physica Sinica. All rights reserved.
  Accession Number: 20220911739640
• Record 364 of
  
  Title:Highly sensitive metal ion sensing by graphene oxide functionalized micro-tapered long-period fiber grating
  
  Author(s):Wang, Ruiduo(1); Kang, Xin(2); Kong, Depeng(1); Jiang, Man(2); Ren, Zhaoyu(2); Hu, Baowen(1); He, Zhengquan(1)
  Source: Analyst  Volume: 147  Issue: 13  DOI: 10.1039/d1an02263f  Published: April 29, 2022  
  Abstract:An accurate as well as highly sensitive label-free chemical sensing platform for the detection of various metal ions was demonstrated. The chemical sensor was derived from the micro-tapered long-period fiber grating (MLPG) by depositing graphene oxide (GO) by chemical-bonding and optical-tweezer effects. The enhancement in refractive index (RI) sensitivity as well as reusability was obtained by evaluating the deposition thickness in the range of approximately 97.7 to 158.9 nm. Based on the analysis of adsorption principles, the enhanced RI sensitivity leads to a limit of detection as low as 3.2 ppb. The highest sensitivities for the cases studied using sodium and manganese ions in a wide concentration range of 1 ppb to 1 × 106 ppb are respectively 2.2 × 10−3 dB per ppb and 3.2 × 10−3 dB per ppb. Mixture samples were also studied to evaluate the properties of sensing the doped ions. This demonstration of GO modified MLPG is bound to find potential applications that require sensing of mixed samples and illustrates significant importance in developing cost-effective, label-free, reusable, and real-time chemical sensors. © 2022 The Royal Society of Chemistry
  Accession Number: 20222412231013
• Record 365 of
  
  Title:Scattered Image Reconstruction at Near-Infrared Based on Spatial Modulation Instability
  
  Author(s):Liao, Yuan(1,2); Li, Lin(1,2); Wang, Zhaolu(1); Huang, Nan(1); Liu, Hongjun(1,3)
  Source: IEEE Photonics Technology Letters  Volume: 34  Issue: 14  DOI: 10.1109/LPT.2022.3185171  Published: July 15, 2022  
  Abstract:We present a method of near-infrared image reconstruction based on spatial modulation instability in a photorefractive strontium barium niobate crystal. The conditions that lead to the formation of modulation instability at near-infrared are discussed depending on the theory of modulation instability gain. Experimental results of scattered image reconstruction at the 1064 nm wavelength show the maximum cross-correlation coefficient and cross-correlation gain are 0.57 and 2.09 respectively. This method is expected to be an aid for near-infrared imaging technologies. © 1989-2012 IEEE.
  Accession Number: 20222812350534
• Record 366 of
  
  Title:In-Plane Anisotropic Plasmons in Van Der Waals Thin Films of WTe2
  
  Author(s):Li, Shaopeng(1); Sun, Qibing(2)
  Source: IEEE Photonics Journal  Volume: 14  Issue: 1  DOI: 10.1109/JPHOT.2022.3146208  Published: February 1, 2022  
  Abstract:Anisotropic plasmonic surface supports elliptic, hyperbolic and even flattened polaritons, which is quite interesting for the diffractionless and highly collimated propagation of infrared light at the nanoscale. However, direct real-space near-field observation of anisotropic plasmons as well as frequency dependent topological transitions in natural materials have not been realized. In this paper, we theoretically investigate real-space anisotropic plasmons in WTe2 thin films by using a phenomenological cavity model, anisotropic near-field plasmonic images with specific interference patterns and isofrequency curves in momentum space have been demonstrated. Due to the frequency selective forbidden of plasmons along b axis, a topological transition from the elliptic to the hyperbolic regime is manifested. Moreover, the plasmons as well as topological transition present significant electrostatic-gating tunability. Our studies provide new insights into WTe2 based plasmonic components for the manipulation of plasmon propagation, which capable of tailoring anisotropic two-dimensional light confinement in the far-infrared regime and can be applied to investigate other anisotropic materials. © 2009-2012 IEEE
  Accession Number: 20220611601242
• Record 367 of
  
  Title:Photon counting three-dimensional imaging with a position sensitive micro-channel plate detector
  
  Author(s):Liu, Yifan(1,2); Sheng, Lizhi(1); Liu, Yongan(1); Zhao, Baosheng(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12169  Issue:   DOI: 10.1117/12.2624010  Published: 2022  
  Abstract:We demonstrate a photon counting three-dimensional radar system based on a micro-channel plate (MCP) detector with a position-sensitive anode. The system is mainly composed of a laser device, a photon counting imaging detector and readout electronics. The probe laser is divided into two channels. One is used to trigger the start signal, and another irradiates the sample. The reflected light enters into the MCP, and it generates the trigger stop signal. The flight time of the laser pulse is obtained through a constant fraction discriminator(CFD) and a time-to-digital converter (TDC). The time resolution can reach the nanosecond level. The distance information of targets at different distances was measured using this system. The results show that the depth resolution of the system is centimeter level. The performance of the system is demonstrated by imaging of a resolution target and a space object. © 2022 SPIE
  Accession Number: 20221611967933
• Record 368 of
  
  Title:Quantitative Phase Retrieval Through Scattering Medium via Compressive Sensing
  
  Author(s):Peng, Tong(1); Li, Runze(1); Min, Junwei(1); Dan, Dan(1); Zhou, Meiling(1); Yu, Xianghua(1); Zhang, Chunmin(2); Bai, Chen(1); Yao, Baoli(1,3)
  Source: IEEE Photonics Journal  Volume: 14  Issue: 1  DOI: 10.1109/JPHOT.2021.3136509  Published: February 1, 2022  
  Abstract:Scattering media, such as biological tissues and turbid liquids, scatter light randomly and introduce several challenges when imaging objects behind them. The transmission matrix (TM) describes the relation between the input and output of a beam transmitted through a medium, which can be used to reconstruct a target located behind a scattering medium. However, the current TM methods cannot easily retrieve the phase distribution of objects inside or behind a scattering medium. In this work, a compressive sensing (CS) method to identify the TM of a scatter contained in an imaging system was investigated. By calibrating the TM, the phase information of the object can be retrieved quantitatively. This method allows one to retrieve multilevel and dynamic phase objects behind different scatters. The influence of the calibration parameters on the reconstruction quality was investigated in detail. The proposed method, featuring noninterference measurements of the TM and exploiting a large field of view, can be used in phase imaging applications. © 2009-2012 IEEE.
  Accession Number: 20215211398083
• Record 369 of
  
  Title:Structured transverse orbital angular momentum probed by a levitated optomechanical sensor
  
  Author(s):Hu, Yanhui(1,2); Kingsley-Smith, Jack J.(1,2); Nikkhou, Maryam(1,2); Sabin, James A.(1,2); Rodríguez-Fortuño, Francisco J.(1,2); Xu, Xiaohao(3); Millen, James(1,2)
  Source: arXiv  Volume:   Issue:   DOI:   Published: September 20, 2022  
  Abstract:The momentum carried by structured light fields exhibits a rich array of surprising features. In this work, we generate transverse orbital angular momentum (TOAM) in the interference field of two parallel and counter-propagating linearly-polarised focused beams, synthesising an array of identical handedness vortices carrying intrinsic TOAM. We explore this structured light field using an optomechanical sensor, consisting of an optically levitated silicon nanorod, whose rotation is a probe of the optical angular momentum, which generates an exceptionally large torque. This simple creation and direct observation of TOAM will have applications in studies of fundamental physics, the optical manipulation of matter and quantum optomechanics. © 2022, CC BY-NC-ND.
  Accession Number: 20220361975
• Record 370 of
  
  Title:Rotating of metallic microparticles with an optimal radially polarized perfect optical vortex
  
  Author(s):Zhou, Yuan(1,2); Zhang, Yanan(1,2); Gao, Wenyu(1,2); Yan, Shaohui(1); Li, Manman(1); Li, Xing(1,2); Wang, Ping(1,3); Yao, Baoli(1,2,4)
  Source: Journal of Optics (United Kingdom)  Volume: 24  Issue: 6  DOI: 10.1088/2040-8986/ac675d  Published: June 2022  
  Abstract:We report an optical rotating of metallic microparticles using an optimal radially polarized perfect optical vortex (RPPOV). Due to its polarization structure, the RPPOV's transverse intensity exhibits two rings separated by roughly a wavelength. We show both numerically and experimentally that a metallic microparticle immersed in such a double-ring vortex develops two radial equilibrium positions, at either of which the particle can experience a non-zero azimuthal force, thus leading to a simultaneous rotation of the metallic microparticles about the optical axis at two orbits with different radius. Furthermore, the rotation radius and velocity can be separately controlled by changing the parameters of the RPPOV. © 2022 IOP Publishing Ltd.
  Accession Number: 20221912098412
• Record 371 of
  
  Title:Dynamics of Bubble Pairs in Water Induced by Focused Nanosecond Laser Pulse
  
  Author(s):Fu, Lei(1,2); Wang, Ping(1,2); Wang, Sijia(1); Xin, Jing(1); Zhang, Luwei(1); Zhang, Zhenxi(1); Wang, Jing(1); Yao, Cuiping(1)
  Source: Zhongguo Jiguang/Chinese Journal of Lasers  Volume: 49  Issue: 4  DOI: 10.3788/CJL202249.0407001  Published: February 25, 2022  
  Abstract:Objective: Focused laser-induced cavitation in liquid is crucial in numerous applications, e.g., targeted cell lysis, microfluidic operations (such as switching, pumping, and mixing), and perforation of cell membranes. Depending on the focusing conditions and laser pulse energy, single or multiple bubble formations may occur, which may be accompanied by bubble coalescence, high-speed jet formation, ring vortex generation, and multiple shock wave emission. Owing to its promising application prospect on microsurgery, micropumping, and tissue cutting, laser-induced multiple bubbles and their interactions have been studied extensively. It has been confirmed that the dynamics of multiple bubbles are strongly related to the relative bubble positions as well as the time and size difference between bubbles. For example, by adjusting these parameters, the strength and direction of the emerging liquid jets can be controlled. Shock wave and rebound bubbles generated after cavitation bubble collapse are susceptible to their asymmetrical collapse. Without a doubt, the mutual interaction of bubbles causes the asymmetrical oscillation process of bubbles. However, to the best of our knowledge, the influence of multiple bubble interactions on shock wave emission and rebound bubble process has not been studied yet. Therefore, in this study, two bubbles with similar sizes were generated using a single nanosecond laser pulse to investigate the influence of relative interval on multiple bubble dynamics, especially on collapse shock wave emission and rebound bubble generation. Methods: A frequency-doubled Q-switched Nd:YAG laser was introduced to generate optical breakdown in water. The laser pulse was split into two parts using a variable beam splitter. Then, the split laser pulses were focused on water from different directions to generate bubble pairs. Three methods were introduced to measure the bubble pair dynamics: high-speed shadowgraph, optical scattering technique, and acoustic detection technique. It was easy to generate bubble pairs with variable relative interval by adjusting the incidence direction of laser pulses, focusing objective position, and pulse energy. First, the bubble pair dynamics with different relative intervals were discussed experimentally and compared with the Rayleigh-Plesset model. Second, the influences of the relative interval between bubble pairs on the collapse shock wave strength and rebound bubble oscillation period were investigated. In this part, a high-speed camera was replaced by an EMCCD to picture the plasmas generated during an optical breakdown, and the bubble size was calculated by its first oscillation period. Results and Discussions: For a single bubble in free liquid, the maximum radius of the bubble linearly increases with the cube root of the pulse energy and its first oscillation period, respectively, (Fig. 3), which means that the bubble size can be calculated from the pulse energy or its first oscillation period. The oscillation process of bubble pairs is significantly influenced by its relative interval (γ) (Fig. 4). For γ=1.36, the bubble pairs oscillates spherically, without contacting each other before their first collapse, but both of their first oscillation periods significantly increases [Figs. 4(a) and (b)]. For γ≈0.49, the two bubbles begin to coalesce during the early stage of expansion, and their shapes deform. The evolution of the equivalent radius of the coalesced bubble fits well with the Rayleigh-Plesset simulation [Figs. 4(c) and (d)]. For γ≈0.18, the coalesced bubble oscillates spherically again during its first period [Figs. 4(e) and (f)], which is similar to the single bubble case. Then, we experimentally examine the influence of relative interval of bubble pairs on the collapse shock wave emission and rebound bubble generation. The results revealed that the first oscillation period was uninfluenced by the relative interval (γ © 2022, Chinese Lasers Press. All right reserved.
  Accession Number: 20221211830543
• Record 372 of
  
  Title:Gap solitons in parity-time symmetric moiré optical lattices
  
  Author(s):Liu, Xiuye(1,2); Zeng, Jianhua(1,2)
  Source: arXiv  Volume:   Issue:   DOI: 10.48550/arXiv.2206.10804  Published: June 21, 2022  
  Abstract:Parity-time (PT) symmetric lattices have been widely studied in controlling the flow of waves, and recently moiré superlattices, connecting the periodic and non-periodic potentials, are introduced for exploring unconventional physical properties in physics; while the combination of both and nonlinear waves therein remains unclear. Here, we report a theoretical survey of nonlinear wave localizations in PT symmetric moiré optical lattices, with the aim of revealing localized gap modes of different types and their stabilization mechanism. We uncover the formation, properties, and dynamics of fundamental and higher-order gap solitons as well as vortical ones with topological charge, all residing in the finite band gaps of the underlying linear-Bloch wave spectrum. The stability regions of the localized gap modes are inspected in two numerical ways: linear-stability analysis and direct perturbed simulations. Our results provide an insightful understanding of solitons physics in combined versatile platforms of PT symmetric systems and moiré patterns. Copyright © 2022, The Authors. All rights reserved.
  Accession Number: 20220213828