Contents 1 Issue (s), 16 Article (s)

Vol.9, Iss.10—Oct.1, 2021 • pp: 1881-2023 Spec. pp:

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Research ArticlesVol.9, Iss.10-Oct..1,2021
Fiber Optics and Optical Communications
Measurement-device-independent quantum key distribution for nonstandalone networks
Guan-Jie Fan-Yuan, Feng-Yu Lu, Shuang Wang, Zhen-Qiang Yin, De-Yong He, Zheng Zhou, Jun Teng, Wei Chen, Guang-Can Guo, and Zheng-Fu Han
Untrusted node networks initially implemented by measurement-device-independent quantum key distribution (MDI-QKD) protocol are a crucial step on the roadmap of the quantum Internet. Considering extensive QKD implementations of trusted node networks, a workable upgrading tactic of existing networks toward MDI networks needs to be explicit. Here, referring to the nonstandalone (NSA) network of 5G, we propose an NSA-MDI scheme as an evolutionary selection for existing phase-encoding BB84 networks. Our solution can upgrade the BB84 networks and terminals that employ various phase-encoding schemes to immediately support MDI without hardware changes. This cost-effective upgrade effectively promotes the deployment of MDI networks as a step of untrusted node networks while taking full advantage of existing networks. In addition, the diversified demands on security and bandwidth are satisfied, and network survivability is improved.
Photonics Research
  • Publication Date: Sep. 06, 2021
  • Vol.9 Issue, 10 10001881 (2021)
Fiber Optics and Optical Communications
Rectangular single-mode polymer optical fiber for femtosecond laser inscription of FBGs
Jitendra Narayan Dash, Xin Cheng, Dinusha Serandi Gunawardena, and Hwa-Yaw Tam
In this study, a novel rectangular polymer single-mode optical fiber for femtosecond (fs) laser-inscribed fiber Bragg gratings (FBGs) is proposed and demonstrated. The cylindrical geometry of the widely used circular fiber elongates the fs laser beam along the fiber axis, resulting in reduced laser intensity and requiring index-matching oil immersion during FBG inscription. However, the flat geometry and negligible surface roughness of the featured fiber significantly diminish this lensing distortion and eliminate the need for oil immersion, thereby resulting in optimal focusing of the laser beam, permitting direct and efficient inscription of FBGs within the optical fiber. The core and cladding of the rectangular fiber were fabricated using two different grades of ZEONEX, a cyclo olefin polymer, which have slightly different refractive indices. The similar glass transition temperature for core and cladding simplifies the fiber drawing process, and a rectangular single-mode optical fiber with dimensions of 213 μm×160 μm and core diameter of 9.4 μm was fabricated using an in-house fiber drawing facility. A second harmonic (520 nm) fs laser beam was used to successfully inscribe a 2-mm-long FBG in the rectangular fiber within a few seconds with a point-by-point technique. The inscription of a single FBG leads to the excitation of higher order FBG peaks at 866.8 and 1511.3 nm, corresponding to widely used wavelength bands in fiber optic sensing. The strain and temperature sensitivities of the FBG were measured to be 7.31 nm/%ε (0.731pm/με) and 10 pm/°C, and 12.95 nm/%ε (1.29 pm/με) and 15 pm/°C at 866.8 nm and 1511.3 nm, respectively.
Photonics Research
  • Publication Date: Sep. 13, 2021
  • Vol.9 Issue, 10 10001931 (2021)
Fiber Optics and Optical Communications
Quantitative in situ measurement of optical force along a strand of cleaved silica optical fiber induced by the light guided therewithin
Mikko Partanen, Hyeonwoo Lee, and Kyunghwan Oh
We propose an optomechanical system to quantify the net force on a strand of cleaved silica optical fiber in situ as the laser light is being guided through it. Four strands of the fiber were bonded to both sides of a macroscopic oscillator, whose movements were accurately monitored by a Michelson interferometer. The laser light was propagating with variable optical powers and frequency modulations. Experimentally, we discovered that the driving force for the oscillator consisted of not only the optical force of the light exiting from the cleaved facets but also the tension along the fiber induced by the light guided therewithin. The net driving force was determined only by the optical power, refractive index of the fiber, and the speed of light, which pinpoints its fundamental origin.
Photonics Research
  • Publication Date: Sep. 16, 2021
  • Vol.9 Issue, 10 10002016 (2021)
Imaging Systems, Microscopy, and Displays
Single-shot 3D tracking based on polarization multiplexed Fourier-phase camera
Jiajie Teng, Chengyang Hu, Honghao Huang, Minghua Chen, Sigang Yang, and Hongwei Chen
For moving objects, 3D mapping and tracking has found important applications in the 3D reconstruction for vision odometry or simultaneous localization and mapping. This paper presents a novel camera architecture to locate the fast-moving objects in four-dimensional (4D) space (x, y, z, t) through a single-shot image. Our 3D tracking system records two orthogonal fields-of-view (FoVs) with different polarization states on one polarization sensor. An optical spatial modulator is applied to build up temporal Fourier-phase coding channels, and the integration is performed in the corresponding CMOS pixels during the exposure time. With the 8 bit grayscale modulation, each coding channel can achieve 256 times temporal resolution improvement. A fast single-shot 3D tracking system with 0.78 ms temporal resolution in 200 ms exposure is experimentally demonstrated. Furthermore, it provides a new image format, Fourier-phase map, which has a compact data volume. The latent spatio-temporal information in one 2D image can be efficiently reconstructed at relatively low computation cost through the straightforward phase matching algorithm. Cooperated with scene-driven exposure as well as reasonable Fourier-phase prediction, one could acquire 4D data (x, y, z, t) of the moving objects, segment 3D motion based on temporal cues, and track targets in a complicated environment.
Photonics Research
  • Publication Date: Sep. 13, 2021
  • Vol.9 Issue, 10 10001924 (2021)
Imaging Systems, Microscopy, and Displays
Quantized Fourier ptychography with binary images from SPAD cameras
Xi Yang, Pavan Chandra Konda, Shiqi Xu, Liheng Bian, and Roarke Horstmeyer
Recently developed single-photon avalanche diode (SPAD) array cameras provide single-photon sensitivity and picosecond-scale time gating for time-of-flight measurements, with applications in LIDAR and fluorescence lifetime imaging. As compared to standard image sensors, SPAD arrays typically return binary intensity measurements with photon time-of-arrival information from fewer pixels. Here, we study the feasibility of implementing Fourier ptychography (FP), a synthetic aperture imaging technique, with SPAD array cameras to reconstruct an image with higher resolution and larger dynamic range from acquired binary intensity measurements. Toward achieving this goal, we present (1) an improved FP reconstruction algorithm that accounts for discretization and limited bit depth of the detected light intensity by image sensors, and (2) an illumination angle-dependent source brightness adaptation strategy, which is sample-specific. Together, these provide a high-quality amplitude and phase object reconstruction, not only from binary SPAD array intensity measurements, but also from alternative low-dynamic-range images, as demonstrated by our simulations and proof-of-concept experiments.
Photonics Research
  • Publication Date: Sep. 15, 2021
  • Vol.9 Issue, 10 10001958 (2021)
Integrated Optics
Hybrid integrated low-noise linear chirp frequency-modulated continuous-wave laser source based on self-injection to an external cavity
Liwei Tang, Hongxiang Jia, Shuai Shao, Sigang Yang, Hongwei Chen, and Minghua Chen
Photonics Research
  • Publication Date: Sep. 15, 2021
  • Vol.9 Issue, 10 10001948 (2021)
Integrated Optics
Proposal and demonstration of a controllable Q factor in directly coupled microring resonators for optical buffering applications
Ying Zhang, Qiang Liu, Chenyang Mei, Desheng Zeng, Qingzhong Huang, and Xinliang Zhang
Optical resonators with controllable Q factors are key components in many areas of optical physics and engineering. We propose and investigate a Q-factor controllable system composed of two directly coupled microring resonators, one of which is tunable and coupled to dual waveguides. By shifting the resonance of the controllable microring, the Q factor of the system as well as the other microring changes significantly. We have demonstrated wide-range controllable Q factors based on this structure in silicon-on-insulator, for example. The influences of spectral detuning and coupling strength between two resonators on the variation of Q factors are studied in detail experimentally. Then, we explore its applications in optical buffering. Tunable fast-to-slow/slow-to-fast light has been carried out by switching the system between the high-Q state and low-Q state. Moreover, optical pulse capture and release are also achievable using this structure with dynamic tuning, and the photon storage properties are investigated. The proposed Q-factor tunable system is simple, flexible, and realizable in various integrated photonic platforms, allowing for potential applications in on-chip optical communications and quantum information processing.
Photonics Research
  • Publication Date: Sep. 16, 2021
  • Vol.9 Issue, 10 10002006 (2021)
Lasers and Laser Optics
Buildup dynamics of multiple solitons in spatiotemporal mode-locked fiber lasers
Kewei Liu, Xiaosheng Xiao, Yihang Ding, Hongyan Peng, Dongdong Lv, and Changxi Yang
Spatiotemporal mode locking is a nonlinear process of multimode soliton self-organization. Here the real-time buildup dynamics of the multiple solitons in a spatiotemporal mode-locked multimode fiber laser are investigated, assisted by the time-stretch technique. We find that the buildup processes are transverse mode dependent, especially during the stages of relaxation oscillation and Q-switching prior to multiple soliton formation. Furthermore, we observe that the transverse modal composition of these generated pulses among the multiple solitons can be different from each other, indicating the spatiotemporal structure of the multiple soliton. A simplified theoretical model based on pulse energy evolution is put forward to interpret the role of 3D saturable absorber on spatiotemporal structures of spatiotemporal mode-locking multiple solitons. Our work has presented the spatiotemporal nonlinear dynamics in multimode fiber lasers, which are novel to those inside the single transverse mode fiber lasers.
Photonics Research
  • Publication Date: Sep. 08, 2021
  • Vol.9 Issue, 10 10001898 (2021)
Nanophotonics and Photonic Crystals
Terahertz wavefront shaping with multi-channel polarization conversion based on all-dielectric metasurface
Jie Li, Chenglong Zheng, Jitao Li, Guocui Wang, Jingyu Liu, Zhen Yue, Xuanruo Hao, Yue Yang, Fuyu Li, Tingting Tang, Yating Zhang, Yan Zhang, and Jianquan Yao
Polarization manipulation of electromagnetic wave or polarization multiplexed beam shaping based on metasurfaces has been reported in various frequency bands. However, it is difficult to shape the beam with multi-channel polarization conversion in a single metasurface. Here, we propose a new method for terahertz wavefront shaping with multi-channel polarization conversion via all-silicon metasurface, which is based on the linear shape birefringence effect in spatially interleaved anisotropic meta-atoms. By superimposing the eigen- and non-eigen-polarization responses of the two kinds of meta-atoms, we demonstrate the possibility for high-efficiency evolution of several typical polarization states with two independent channels for linearly polarized waves. The measured polarization conversion efficiency is higher than 70% in the range of 0.9–1.3 THz, with a peak value of 89.2% at 1.1 THz. In addition, when more other polarization states are incident, combined with the integration of sub-arrays, we can get more channels for both polarization conversion and beam shaping. Simulated and experimental results verify the feasibility of this method. The proposed method provides a new idea for the design of terahertz multi-functional metadevices.
Photonics Research
  • Publication Date: Sep. 13, 2021
  • Vol.9 Issue, 10 10001939 (2021)
Optical and Photonic Materials
Ultrastable Gd3+ doped CsPbCl1.5Br1.5 nanocrystals blue glass for regulated and low thresholds amplified spontaneous emission
Qingyun He, Enrou Mei, Ze Wang, Xiaojuan Liang, Suqin Chen, and Weidong Xiang
Here, Gd-doped CsPbCl1.5Br1.5 nanocrystals (NCs) in borosilicate glass matrix (B2O3-SiO2-ZnO) were prepared by melting quenching and in-situ crystallization. The optical performance of CsPbCl1.5Br1.5 NCs glasses under different heat-treatment temperatures and the content of Gd3+ were analyzed in detail. After CsPbCl1.5Br1.5 NCs glass is doped with Gd3+ ions, the photoluminescence intensity increases and the synthesized Gd-doped CsPbCl1.5Br1.5 NCs glasses have excellent water stability and thermal cycling performance. In addition, the influence of Gd-doped concentrations and heat-treatment temperatures on the amplified spontaneous emission (ASE) thresholds of CsPbCl1.5Br1.5 NCs glasses was studied, and the Gd-doped CsPbCl1.5Br1.5 NCs glasses achieve controllable ASE thresholds at room temperature. The ASE threshold can be as low as 0.39 mJ/cm2. This work offers a neoteric reference for the research in the application of metal ion-doped perovskite NCs and a new idea for the realization of controllable and low ASE thresholds on perovskite NCs.
Photonics Research
  • Publication Date: Sep. 09, 2021
  • Vol.9 Issue, 10 10001916 (2021)
Optical Devices
Very large group delay in VHF band using coupled high temperature superconducting resonators
Tianning Zheng, Bin Wei, Fuchuan Lei, and Bisong Cao
Storing a very high frequency (VHF) band (30–300 MHz) electromagnetic wave has many potential applications, such as phase modulation, buffering, and radio frequency memory. It can be effectively achieved by applying coupled resonator-based electromagnetically induced transparency (EIT) due to its slow light effect. However, the wavelength in the VHF band is too long to design resonators, and the group delay is limited by the high resistive loss of metal. The practical application of EIT in the VHF band is still a big challenge. In this work, we propose and experimentally demonstrate EIT response in a high-temperature superconducting (HTS) microwave circuit with coupled-resonator-induced transparency. The chip size of the HTS circuit is only 34 mm×20 mm with a very low transparency frequency of 198.55 MHz. In addition, we implement very large group delay higher than 12.3 μs and 16.2 μs with working temperatures of 65 K and 50 K separately, which is much longer than the previous reported works on slow wave. The fabricated circuit is planar with working temperature about 65 K, and thus can be easily integrated into other microwave devices under the cryogenic conditions provided by a commercial portable Stirling cryocooler. Our proposed method paves a way for studying EIT in the microwave region due to the high quality factor of the HTS resonator, which has great potential use for radio-frequency memory in the future.
Photonics Research
  • Publication Date: Sep. 08, 2021
  • Vol.9 Issue, 10 10001892 (2021)
Optical Devices
Direct laser writing spiral Sagnac waveguide for ultrahigh magnetic field sensing
Dengwei Zhang, Zhihang Zhang, Heming Wei, Jianrong Qiu, and Sridhar Krishnaswamy
A high-birefringence spiral Sagnac waveguide (SSW) device fabricated via direct laser writing (DLW) using a two-photon polymerization (2PP) technique is proposed, designed, and experimentally demonstrated as an ultrahigh magnetic field sensor. The sensor comprises a Y-style tapered waveguide and an SSW containing two microfluidic channels. The SSW has a total length of 2.4 mm and a spiral radius of 200 μm. Due to the asymmetric structure, the SSW has a high birefringence of 0.016, which can be designed as a magnetic field sensor, as a magnetic fluid can be filled into the microfluidic channel changing the guiding mode and the birefringence and consequently leading to a change in phase of the interferometer when the applied magnetic field changes. The experimental results show that the proposed photonic device has a sensitivity to magnetic fields as high as 0.48 nm/Oe within a range from 10 to 100 Oe. The proposed device is very stable and easy to fabricate, and it can therefore be used for weak magnetic field detection.
Photonics Research
  • Publication Date: Sep. 16, 2021
  • Vol.9 Issue, 10 10001984 (2021)
Optoelectronics
Multiple-quantum-well-induced unipolar carrier transport multiplication in AlGaN solar-blind ultraviolet photodiode
Long Guo, Ke Jiang, Xiaojuan Sun, Zihui Zhang, Jianwei Ben, Yuping Jia, Yong Wang, and Dabing Li
AlGaN solar-blind ultraviolet (SBUV) detectors have potential application in fire monitoring, corona discharge monitoring, or biological imaging. With the promotion of application requirements, there is an urgent demand for developing a high-performance vertical detector that can work at low bias or even zero bias. In this work, we have introduced a photoconductive gain mechanism into a vertical AlGaN SBUV detector and successfully realized it in a p-i-n photodiode via inserting a multiple-quantum-well (MQW) into the depletion region. The MQW plays the role of trapping holes and increasing carrier lifetime due to its strong hole confinement effect and quantum confinement Stark effect. Hence, the electrons can go through the detector multiple times, inducing unipolar carrier transport multiplication. Experimentally, an AlGaN SBUV detector with a zero-bias peak responsivity of about 0.425 A/W at 233 nm is achieved, corresponding to an external quantum efficiency of 226%, indicating the existence of internal current gain. When compared with the device without MQW structure, the gain is estimated to be about 103 in magnitude. The investigation provides an alternative and effective approach to obtain high current gain in vertical AlGaN SBUV detectors at zero bias.
Photonics Research
  • Publication Date: Sep. 08, 2021
  • Vol.9 Issue, 10 10001907 (2021)
Optoelectronics
Highly efficient transparent quantum-dot light-emitting diodes based on inorganic double electron-transport layers
Nan Zhang, Xiangwei Qu, Quan Lyu, Kai Wang, and Xiao Wei Sun
Herein, we report the fabrication of high-performance transparent quantum-dot light-emitting diodes (Tr-QLEDs) with ZnO/ZnMgO inorganic double electron-transport layers (ETLs). The ETLs effectively suppress the excess electron injection and facilitate charge balance in the Tr-QLEDs. The thick ETLs as buffer layers can also withstand the plasma-induced damage during the indium tin oxide sputtering. These factors collectively contribute to the development of Tr-QLEDs with improved performance. As a result, our Tr-QLEDs with double ETLs exhibited a high transmittance of 82% at 550 nm and a record external quantum efficiency of 11.8%, which is 1.27 times higher than that of the devices with pure ZnO ETL. These results indicate that the developed ZnO/ZnMgO inorganic double ETLs could offer promising solutions for realizing high-efficiency Tr-QLEDs for next-generation display devices.
Photonics Research
  • Publication Date: Sep. 15, 2021
  • Vol.9 Issue, 10 10001979 (2021)
Quantum Optics
Characterization and stability measurement of deployed multicore fibers for quantum applications
Davide Bacco, Nicola Biagi, Ilaria Vagniluca, Tetsuya Hayashi, Antonio Mecozzi, Cristian Antonelli, Leif K. Oxenløwe, and Alessandro Zavatta
Multicore fibers are expected to be a game-changer in the coming decades thanks to their intrinsic properties, allowing a larger transmission bandwidth and a lower footprint in optical communications. In addition, multicore fibers have recently been explored for quantum communication, attesting to their uniqueness in transporting high-dimensional quantum states. However, investigations and experiments reported in literature have been carried out in research laboratories, typically making use of short fiber links in controlled environments. Thus, the possibility of using long-distance multicore fibers for quantum applications is still to be proven. We characterize here for the first time, to the best of our knowledge, in terms of phase stability, multiple strands of a four-core multicore fiber installed underground in the city of L’Aquila, with an overall fiber length up to about 25 km. In this preliminary study, we investigate the possibility of using such an infrastructure to implement quantum-enhanced schemes, such as high-dimensional quantum key distribution, quantum-based environmental sensors, and more, in general, quantum communication protocols.
Photonics Research
  • Publication Date: Sep. 16, 2021
  • Vol.9 Issue, 10 10001992 (2021)
Quantum Optics
Narrowband photonic quantum entanglement with counterpropagating domain engineering
Yi-Chen Liu, Dong-Jie Guo, Ran Yang, Chang-Wei Sun, Jia-Chen Duan, Yan-Xiao Gong, Zhenda Xie, and Shi-Ning Zhu
Photonics Research
  • Publication Date: Sep. 16, 2021
  • Vol.9 Issue, 10 10001998 (2021)