2020

• Record 445 of
  
  Title:Binary amplitude-only image reconstruction through a MMF based on an AE-SNN combined deep learning model
  
  Author(s):Chen, Hui(1,2,3); He, Zhengquan(1); Zhang, Zaikun(1,2); Geng, Yi(1,2); Yu, Weixing(3)
  Source: Optics Express  Volume: 28  Issue: 20  DOI: 10.1364/OE.403316  Published: September 28, 2020  
  Abstract:The obstacle of imaging through multimode fibers (MMFs) is encountered due to the fact that the inherent mode dispersion and mode coupling lead the output of the MMF to be scattered and bring about image distortions. As a result, only noise-like speckle patterns can be formed on the distal end of the MMF. We propose a deep learning model exploited for computational imaging through an MMF, which contains an autoencoder (AE) for feature extraction and image reconstruction and self-normalizing neural networks (SNNs) sandwiched and employed for high-order feature representation. It was demonstrated both in simulations and in experiments that the proposed AE-SNN combined deep learning model could reconstruct image information from various binary amplitude-only targets going through a 5-meter-long MMF. Simulations indicate that our model works effectively even in the presence of system noise, and the experimental results prove that the method is valid for image reconstruction through the MMF. Enabled by the spatial variability and the self-normalizing properties, our model can be generalized to solve varieties of other computational imaging problems. © 2020 OSA - The Optical Society. All rights reserved.
  Accession Number: 20204109337141
• Record 446 of
  
  Title:Optical trapping and manipulating with a silica microring resonator in a self-locked scheme
  
  Author(s):Ho, Victor W.L.(1); Chang, Yao(2); Liu, Yang(2); Zhang, Chi(2); Li, Yuhua(1); Davidson, Roy R.(3); Little, Brent E.(4); Wang, Guanghui(2); Chu, Sai T.(1)
  Source: Micromachines  Volume: 11  Issue: 2  DOI: 10.3390/mi11020202  Published: February 1, 2020  
  Abstract:Based on the gradient force of evanescent waves in silica waveguides and add-drop micro-ring resonators, the optical trapping and manipulation of micro size particles is demonstrated in a self-locked scheme that maintains the on-resonance system even if there is a change in the ambient temperature or environment. The proposed configuration allows the trapping of particles in the high Q resonator without the need for a precise wavelength adjustment of the input signal. On the one hand, a silicon dioxide waveguide having a lower refractive index and relatively larger dimensions facilitates the coupling of the laser with a single-mode fiber. Furthermore, the experimental design of the self-locked scheme reduces the sensitivity of the ring to the environment. This combination can trap the micro size particles with a high stability while manipulating them with high accuracy. © 2020 by the author.
  Accession Number: 20201108296121
• Record 447 of
  
  Title:Incoherent, non-invasive and non-scanning superoscillation-based microscope for super-resolution imaging
  
  Author(s):Xie, Qingkun(1,3); Jiang, Yanru(1,3); Liang, Jian(1); Qu, Enshi(1); Ren, Liyong(2)
  Source: Optics Communications  Volume: 463  Issue:   DOI: 10.1016/j.optcom.2020.125445  Published: 15 May 2020  
  Abstract:The superoscillation phenomenon, since it was first observed in the time variation of quantum systems, has become a research hotspot in optics. Recently, it has been vividly presented that one could achieve far field super-resolution imaging using a superoscillation lens instead of a conventional lens. Notwithstanding, confined by the coherent illumination and the complex scanning imaging mechanism, those systems have serious drawbacks in large field super-resolution imaging, such as the off-axis deformation, low imaging speed and strong sidelobe noise. In this paper, we report an incoherent, non-invasive and no-scanning superoscillation based microscope with a small numerical aperture, which, in principle, could effectively alleviate those limitations. We verify that, by installing a superoscillation element behind an imaging lens, a sub-diffraction point spread function with strongly suppressed sidelobes can be obtained. The experimental results of complex targets imaging demonstrate its feasibility and effectiveness in far field non-scanning imaging, where targets with detailed structures smaller than 71% of the Rayleigh Criterion are well distinguished. © 2020 Elsevier B.V.
  Accession Number: 20200608148110
• Record 448 of
  
  Title:Resist-free nanoimprinting on optical fibers for plasmonic optrodes
  
  Author(s):Jia, Peipei(1,2); Kong, Depeng(3); Ebendorff-Heidepriem, Heike(1)
  Source: Applied Materials Today  Volume: 20  Issue:   DOI: 10.1016/j.apmt.2020.100751  Published: September 2020  
  Abstract:Nanostructure patterning on optical fibers enables miniaturized optrodes for photonic and plasmonic applications. Here we report a direct nanoimprint technique to produce high-quality nanostructure arrays on optical fiber endfaces. It has only one single step: imprinting optical fiber tips against a mold with nanostructures at the elevated temperature. This new method abandons resist used in traditional fiber-imprinting methods. Hundreds of fibers can be shaped simultaneously with one mold within minutes. The imprinted nanostructure arrays on optical fibers are transformed into plasmonic optrodes through metal deposition. Variation of imprint depths and mold patterns allows tailoring of the plasmonic resonances of these nanostructure arrays for high-performance refractometric sensing and on-fiber polarization. The sensitivity of 690 nm/RIU and figure of merit of 50 are both among the highest values for similar plasmonic nanostructure arrays. This resist-free nanoimprint paves the way towards a low-cost and high-throughput realization of plasmonic optrodes and their wide applications. © 2020
  Accession Number: 20202808907980
• Record 449 of
  
  Title:Long modal interference in multimode fiber and its application in vital signs monitoring
  
  Author(s):Xu, Wei(1,2); Shen, Ying(3); Yu, Changyuan(4); Dong, Bo(1,2,5); Zhao, Wei(1,2,5); Wang, Yishan(1,2,5)
  Source: Optics Communications  Volume: 474  Issue:   DOI: 10.1016/j.optcom.2020.126100  Published: 1 November 2020  
  Abstract:All-fiber vital signs monitoring based on long-modal-interference (LMI) in multimode fiber (MMF) is proposed and investigated theoretically and experimentally. The LMI-MMF is simply formed by splicing of a two-meter-long MMF and two single mode fibers (SMFs) with core-offsets at splicing joints. It is worth mentioning that all fibers that used are sheathed with 900-μm protection sleeve. Core-offset dependency of vital signs monitoring performance is specifically analyzed. Experiments are carried out on subjects with weight from 56 kg to 103 kg without further optimization or modification. Compared with commercial piezoceramic-based respiratory sensor and SpO2-based heartbeat sensor, the proposed non-wearable all-fiber vital signs monitoring sensor based on LMI-MMF shows great consistence with high Person's correlation coefficient. It is the first time to put forward the LMI-MMF-based fiber sensor and apply it to realize the non-wearable vital signs monitoring. Specific superiorities of low cost, real time and non-intrusiveness make it potentially competitive in household healthcare and other medical fields. © 2020 Elsevier B.V.
  Accession Number: 20202208759915
• Record 450 of
  
  Title:Development of low-loss lead-germanate glass for mid-infrared fiber optics
  
  Author(s):Wang, Pengfei(1); Ebendorff-Heidepriem, Heike(2)
  Source: 2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings  Volume:   Issue:   DOI: 10.1364/CLEOPR.2020.C7H_2  Published: August 2020  
  Abstract:We report the understanding of the factors (gas types, flow rate, dehydration agents, etc.) that determine dehydration efficiency and metallic Pb formation during the lead-germanate glass melting process, as well as the fabrication of low loss lead-germanate glass fiber through extrusion method. © 2020 IEEE.
  Accession Number: 20205209687886
• Record 451 of
  
  Title:Chip-based tunable all-optical logic gates via four-wave mixing in graphene-on-silicon microresonators
  
  Author(s):Wu, Wei(1,2); Sun, Qibing(1,3); Wang, Guoxi(1,2); Zhang, Lingxuan(1,3); Zhao, Wei(1,2)
  Source: Optics InfoBase Conference Papers  Volume:   Issue:   DOI: null  Published: October 24, 2020  
  Abstract:We present a practical tunable all-optical logic gate based on the FWM effect in the graphene-on-silicon (GoS) microresonator. The GoS microresonator could produce broadband flat dispersion with multiple zero-dispersion wavelengths (ZDWs) by electrically tuning the graphene. © OSA 2020, © 2020 The Author(s)
  Accession Number: 20211110067690
• Record 452 of
  
  Title:Highly sensitive smart cushion embedded with SMS structure for contactless vital signs and activity monitoring
  
  Author(s):Han, Shuying(1); Xu, Wei(2); You, Shanhong(1); Dong, Bo(2); Yu, Changyuan(3,4); Zhao, Wei(2,5); Wang, Yishan(2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11547  Issue:   DOI: 10.1117/12.2573877  Published: 2020  
  Abstract:A smart cushion based on single-mode-fiber-multimode-fiber-single-mode-fiber (SMS) with core-offset splicing, which can simultaneously realize human vital signs monitoring and activity monitoring, is proposed and experimentally demonstrated. The SMS structure is sandwiched between a piece of fiberglass mesh and a polyvinyl chloride (PVC) layer and then embedded in a common home or office cushion, which is the component of the proposed cushion. When people sit on the cushion placed on a chair, micro-strain induced by human activity including respiration, heartbeat and body movement will change the output light intensity of the fiber structure. By signal processing algorithms including filtering, fast Fourier transform (FFT) and feature extraction, the respiration rate (RR) and heartbeat rate (HR) can be obtained and human activity state on the cushion including nobody state, movement state and normal state can be judged. Furthermore, the performances of two memory foam cushions with different thicknesses are compared and proven to be both available. Such a smart portable cushion can realize real-time, noninvasive and highly sensitive monitoring of vital signs and activities within the accuracy of one second, especially for the elderly in nursing homes and office workers. © 2020 SPIE.
  Accession Number: 20204809536304
• Record 453 of
  
  Title:Continuous scanning 3D imaging with SPAD array based on pixel multiplexing
  
  Author(s):Kang, Yan(1); Xue, Ruikai(1,2); Li, Lifei(1); Zhang, Tongyi(1,2); Zhang, Yong(3); Zhao, Wei(1,2)
  Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering  Volume: 49  Issue:   DOI: 10.3788/IRLA20200375  Published: November 25, 2020  
  Abstract:Lidar systems based on single-photon avalanched diode (SPAD) array detector not only have high sensitivity and time resolution, but also have high detection rate. It has wide application prospects in the fields of remote sensing mapping, target recognition, spacecraft landing and so on. Due to the shortcomings of the current SPAD array devices, such as the small pixel format and the hot pixel problems, the quality of the three-dimensional (3D) images obtained by directly using the SPAD array is poor and the imaging area is small. A continuous scanning three-dimensional imaging method with SPAD array based on pixel multiplexing was proposed to expand the imaging area. At the same time, the multiplexing of pixel information could increase the cumulative detection times of the same target point, thereby improving the depth measurement accuracy and the 3D imaging quality. A push-broom imaging experimental system was established based on a 32 ×32 SPAD array. By performing a one-dimensional continuous scanning imaging experiment on a target 3.3 m away, a fast and large-scale photon counting 3D imaging (32 rows ×520 columns/7 s) was achieved. Meanwhile, the influence of hot pixels on the imaging results is effectively alleviated, and the plane accuracy of the three-dimensional image achieves 2.3 mm. © 2020, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.
  Accession Number: 20210209756978
• Record 454 of
  
  Title:Isolated Attosecond Pulse with 159 as Duration Measured by Home Built Attosecond Streaking Camera
  
  Author(s):Wang, Xianglin(1); Xu, Peng(1,3); Li, Jie(2,3); Yuan, Hao(1,3); Bai, Yonglin(1); Wang, Yishan(1); Zhao, Wei(1)
  Source: Zhongguo Jiguang/Chinese Journal of Lasers  Volume: 47  Issue: 4  DOI: 10.3788/CJL202047.0415002  Published: April 10, 2020  
  Abstract:In order to accurately measure the characteristics of attosecond pulses, we have independently developed a set of attosecond streaking camera with high energy resolution. The device adopts an electronic time-of-flight spectrometer with a magnetic bottle structure and an electronic flight distance of up to 2 m. Based on the above design, the spectrometer has high energy resolution and collection efficiency. The stability accuracy of delayed scanning of NIR femtosecond pulses and XUV attosecond pulses is smaller than 20 as (root-mean-square) in optical system of the device. A double optical gating technology was used to shape the optical electric field of the femtosecond pulses, and an isolated attosecond pulse was generated in the Ne gas cell. The attosecond streaking spectrogram was obtained by the attosecond streaking camera. An isolated 159-as attosecond pulse was achieved through phase retrieval by omega oscillation filtering (PROOF). © 2020, Chinese Lasers Press. All right reserved.
  Accession Number: 20202308782432
• Record 455 of
  
  Title:Time-resolved characteristics of laser induced breakdown spectroscopy on non-flat samples by single beam splitting
  
  Author(s):Lei, Bingying(1,2); Xu, Boping(1); Wang, Jing(1,2); Li, Jing(1,2); Wang, Yishan(1,2); Tang, Jie(1,2); Zhao, Wei(1,2); Duan, Yixiang(3)
  Source: RSC Advances  Volume: 10  Issue: 65  DOI: 10.1039/d0ra06582j  Published: October 28, 2020  
  Abstract:A single-beam-splitting approach was used to enhance the signal intensity of LIBS under the extreme conditions of laser beam grazing of the surface of non-flat samples. Time-resolved spectra show that the laser-ablated plasma presents a stronger spectral intensity and a slower plasma decay in the split beam mode because of the higher laser irradiance. The temporal evolutions of signal enhancement factors indicate that the enhancement effect first rises and then drops with delay time and the maximum enhancement factor of Al plasma comes later than that of Cu plasma under the same laser energy. The mechanisms behind it are discussed. It is also found that the electron density exhibits a faster decay with delay time in the split beam mode, mainly due to the faster plasma expansion. And a slower increase of electron density with laser energy is observed in the split beam mode because of the plasma shielding effect. This journal is © The Royal Society of Chemistry.
  Accession Number: 20204609489661
• Record 456 of
  
  Title:Graphene-assisted high-precision temperature sensing by long-period fiber gratings
  
  Author(s):Wang, Ruiduo(1,2); Ren, Zhaoyu(3); Kong, Xudong(1,2); Kong, Depeng(1); Hu, Baowen(1); He, Zhengquan(1)
  Source: Journal of Physics D: Applied Physics  Volume: 53  Issue: 6  DOI: 10.1088/1361-6463/ab5498  Published: 2020  
  Abstract:The tapered long-period fiber grating (TLPFG) and rotated chiral long-period fiber gratings (CLPFG) heated by a CO2 laser were fabricated by periodically tapering and rotating standard single-mode fibers (SMF). The temperature sensing characteristics of the TLPFG and CLPFG between 30 °C and 60 °C were experimentally investigated, and the slopes of the wavelength shift corresponded to 0.115 nm °C-1 and 0.04 nm °C-1, respectively. The graphene films were coated on gratings to fabricate graphene-coated TLPFG (GTLPFG) and graphene-coated CLPFG (GCLPFG). Given the thermal effects of graphene, the slopes of the resonance dip shift of the GTLPFG and GCLPFG between 30 °C and 60 °C increased to 0.196 nm °C-1 and 0.113 nm °C-1, respectively. Additionally, the high temperature sensing properties of TLPFG and CLPFG between 100 °C and 1000 °C were investigated. The slopes of the higher-order resonance dips of the TLPFG and CLPFG corresponded to 0.119 nm °C-1 and 0.09 nm °C-1, respectively, during the heating process, and to 0.116 °C-1 and 0.09 nm °C-1, respectively, during the cooling process. In the low and high temperature zones, the TLPFG exhibited higher sensitivity when compared to that of the CLPFG, while the CLPFG exhibited higher sensing precision with linearity approaching 1. Given the simple and unsophisticated fabrication process and the high quality and sensitivity of the fabricated gratings, the proposed sensors can play an important role in high-precision temperature-sensing applications. © 2019 IOP Publishing Ltd.
  Accession Number: 20200308033227