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Gate-tunable high-performance broadband phototransistor array of two-dimensional PtSe_(2) on SOI

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Nano Research 2023年第5期16卷 7559-7567页

作者： Yexin Chen Qinghai Zhu Xiaodong Zhu Yijun Sun Zhiyuan Cheng Jing Xu Mingsheng Xu School of Micro-Nano Electronics State Key Laboratory of Silicon MaterialsZhejiang UniversityHangzhou 310027China State key laboratory of Silicon Materials School of Materials Science and EngineeringZhejiang UniversityHangzhou 310027China College of Information Science&Electronic Engineering Zhejiang UniversityHangzhou 310027China key laboratory of ocean observation-imaging testbed of zhejiang province Ocean CollegeZhejiang UniversityZhoushan 316021China

Two-dimensional(2D)layered materials have attracted extensive research interest in the field of high-performance photodetection due to their high carrier mobility,tunable bandgap,stability,other excellent ***,we propose a gate-tunable,high-performance,self-driving,wide detection range phototransistor based on a 2D PtSe_(2)on silicon-oninsulator(SOI).Benefiting from the strong built-in electric field of the PtSe_(2)/Si heterostructure,the phototransistor has a fast response time(rise/fall time)of 36.7/32.6μ*** PtSe_(2)/Si phototransistor exhibits excellent photodetection performance over a broad spectral range from ultraviolet to near-infrared,including a responsivity of 1.07 A/W and a specific detectivity of 6.60×10^(9)Jones under 808 nm illumination at zero gate *** responsivity and specific detectivity of PtSe_(2)/Si phototransistor at 5 V gate voltage are increased to 13.85 A/W and 1.90×10^(10) Jones under 808 nm ***,the fabricated PtSe_(2)/Si phototransistor array shows excellent uniformity,reproducibility,long-term stability in terms of photoresponse performance with negligible variation between pixel *** architecture of present PtSe_(2)/Si on SOI platform paves a new way of a general strategy to realize high-performance photodetectors by combining the advantages of both 2D materials and conventional semiconductors which is compatible with current Si-complementary metal oxide semiconductor(CMOS)process.

关键词： two-dimensional PtSe_(2) silicon-on-insulator(SOI) heterojunction phototransistor gate voltage modulation

Tracking of time-evolving sound speed profiles with an auto-regressive state-space model

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Chinese Journal of Acoustics 2017年第3期36卷 302-312页

作者： JIN Liling LI Jianlong XU Wen College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027 key laboratory of ocean observation-imaging testbed of zhejiang province Hangzhou 310027

An approach for time-evolving sound speed profiles tracking in shallow water is discussed. The inversion of time-evolving sound speed profiles is modeled as a state-space estimation problem, which includes a state equation for predicting the time-evolving sound speed profile and a measurement equation for incorporating local acoustic measurements. In the paper, auto-regression （AR） method is introduced to obtain a high-order AR evolution model of the sound speed field time variations, and the ensemble Kalman filter is utilized to track the sound speed field. To validate the approach, the accuracy in sound speed estimation is analyzed via a numerical implementation using the ASIAEX experimental environment and the sound velocity measurement data. Compared with traditional approaches based on the state evolution represented as a random walk, simulation results show the proposed AR method can effectively reduce the tracking errors of sound speed, and still keep good tracking performance at low signal-to-noise ratios.

关键词： time Tracking of time-evolving sound speed profiles with an auto-regressive state-space model SSP EnKF AR

Data Concurrent Transmission MAC Protocol for Application Oriented Underwater Acoustic Sensor Networks

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China Communications 2022年第10期19卷 220-237页

作者： Xiaoxiao Zhuo Hong Yang Meiyan Liu Yan Wei Guanding Yu Fengzhong Qu The key laboratory of ocean observation-imaging testbed of zhejiang province Zhejiang UniversityZhoushan 316021China The Engineering Research Center of oceanic Sensing Technology and Equipment Ministry of EducationZhejiang UniversityZhoushan 316021China The College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China

With the increasing demand for marine exploration, underwater acoustic sensor networks (UASNs) are prone to have the characteristics of large-scale, long term monitoring, and high data traffic load. Underwater media access control (MAC) protocols, which allow multiple users to share the common medium fairly and efficiently, are essential for the performance of UASNs. However, the design of MAC protocols is confronted with the challenges of spatial unfairness, data eruption, and low energy efficiency. In this paper, we propose a novel data concurrent transmission (DCT) MAC protocol, which is able to exploit long propagation delay and conduct concurrent transmission. Specifically, we present the theoretical performance analysis of the proposed MAC protocol in detail and give an analytical solution of the success concurrent transmission probability between nodes. In addition, simulation results are provided to demonstrate that our proposed protocol is appropriate for UASNs and can significantly improve the performance in terms of network throughput and energy consumption. Finally, we give some typical future applications of UASNs and discuss the demands on MAC protocol design.

关键词： underwater acoustic sensor networks MAC protocols data concurrent transmission

Underwater wireless optical communication:why, what, and how? [Invited]

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Chinese Optics Letters 2019年第10期17卷 34-43页

作者： Jing Xu Optical Communications laboratory Ocean CollegeZhejiang UniversityZhoushan 316021China key laboratory of ocean observation-imaging testbed of zhejiang province Ocean CollegeZhejiang UniversityZhoushan 316021China

Foreseeing the proliferation of underwater vehicles and sensors,underwater wireless optical communication(UWOC)is a key enabler for ocean exploration,with strong competitiveness in short-range bandwidth-intensive *** provide a tutorial on the basic concepts and essential features of UWOC,as well as an overview of work being conducted in this *** challenges,arising from the characteristics of underwater channels,and possible roadmaps are discussed in *** review is expected to be of great use for the link designers of this field.

关键词： communication optical wireless

Security enhancement for OFDM-UWOC system using three-layer chaotic encryption and chaotic DFT precoding

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Chinese Optics Letters 2022年第11期20卷 7-13页

作者： Huan Deng Zihao Du Jianmin Xiong Xingqi Yang Yan Hua Jing Xu Optical Communications laboratory Ocean CollegeZhejiang UniversityZhoushan 316021China key laboratory of ocean observation-imaging testbed of zhejiang province Ocean CollegeZhejiang UniversityZhoushan 316021China

Security is one of the key issues in communications,but it has not attracted much attention in the field of underwater wireless optical communication(UWOC).This Letter proposes a UWOC encryption scheme with orthogonal frequency division multiplexing(OFDM)modulation,based on the three-layer chaotic encryption and chaotic discrete Fourier transform(DFT)*** three-layer chaotic encryption processes are bit stream diffusion,in-phase/quadrature encryption,and time-frequency *** multi-fold data encryption,the scheme can create a keyspace of 9.7×10^(179),effectively resisting brute force attacks and chosen-plaintext attacks.A 3 Gbit/s encrypted OFDM signal is successfully transmitted over a 7 m water channel.

关键词： security underwater wireless optical communication chaotic encryption chosen-plaintext attacks

Superscattering of water waves

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National Science Review 2023年第7期10卷 91-97页

作者： Zijian Qin Chao Qian Lian Shen Xiaoping Wang Ido Kaminer Hongsheng Chen Huaping Wang key laboratory of ocean observation-imaging testbed of zhejiang province Institute of Marine Electronics Engineering Ocean College Zhejiang University ZJU-Hangzhou Global Science and Technology Innovation Center Key Lab.of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Zhejiang University ZJU-UIUC Institute Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation Zhejiang University Jinhua Institute of zhejiang University Zhejiang University Department of Electrical Engineering Technion-Israel Institute of Technology

Inspired by the concept of superscattering in optics,we for the first time theoretically predict and experimentally demonstrate the superscattering phenomenon in water *** subwavelength superscatterer is constructed by multi-layered concentric cylinders with an inhomogeneous depth *** superscatterer breaks the long-held single-channel scattering limit by several times and thus significantly enhances the total scattering *** underlying mechanism originates from the near degeneracy of the resonances of multiple *** fabricate the superscatterer prototype and experimentally measure the near-field patterns,which are consistent with theoretical prediction and numerical *** study opens a new avenue to strengthen water-wave scattering and deepen the understanding in water waves,which can be useful for ocean energy harvesting and harbor protection.

关键词： superscattering water wave metamaterials

Acoustic localization with multi-layer isogradient sound speed profile using TDOA and FDOA

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Frontiers of Information Technology & Electronic Engineering 2023年第1期24卷 164-175页

作者： Dongzhou ZHAN Sitian WANG Shougui CAI Huarong ZHENG Wen XU College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China key laboratory of ocean observation-imaging testbed of zhejiang province Ocean CollegeZhejiang UniversityZhoushan 316021China

In the underwater medium,the speed of sound varies with water depth,temperature,and *** inhomogeneity of water leads to bending of sound rays,making the existing localization algorithms based on straightline propagation less *** realize high-precision node positioning in underwater acoustic sensor networks(UASNs),a multi-layer isogradient sound speed profile(SSP)model is developed using the linear segmentation approximation ***,the sound ray tracking problem is converted into a polynomial root-searching *** on the derived gradient of the signal’s Doppler shift at the sensor node,a novel underwater node localization algorithm is proposed using both the time difference of arrival(TDOA)and frequency difference of arrival(FDOA).Simulations are implemented to illustrate the effectiveness of the proposed *** with the traditional straight-line propagation method,the proposed algorithm can effectively handle the sound ray bending *** accuracy with different SSP modeling errors is also ***,accurate and reliable node localization can be achieved.

关键词： Underwater acoustic sensor network Acoustic localization Sound speed profile Time difference of arrival(TDOA) Frequency difference of arrival(FDOA)

Enhanced imaging through turbid water based on quadrature lock-in discrimination and retinex aided by adaptive gamma function for illumination correction

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Chinese Optics Letters 2023年第10期21卷 24-29页

作者： Riffat Tehseen Amjad Ali Mithilesh Mane 葛文敏李燕龙张泽君徐敬 Optical Communication laboratory Ocean CollegeZhejiang UniversityZhoushan 316021China Hainan Institute of zhejiang University Sanya 572000China key laboratory of ocean observation-imaging testbed of zhejiang province Ocean CollegeZhejiang UniversityZhoushan 316021China

This paper presents an improved method for imaging in turbid water by using the individual strengths of the quadrature lock-in discrimination(QLD)method and the retinex *** first,the high-speed QLD is performed on images,aiming at capturing the ballistic ***,we perform the retinex image enhancement on the QLD-processed images to enhance the contrast of the ***,the effect of uneven illumination is suppressed by using the bilateral gamma function for adaptive illumination *** experimental results depict that the proposed approach achieves better enhancement than the existing approaches,even in a high-turbidity environment.

关键词： quadrature lock-in discrimination clear vision scattering retinex uneven illumination

Delay-Doppler deconvolution image formation for multiple targets in waveguide environment

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Chinese Journal of Acoustics 2017年第4期36卷 473-488页

作者： ZHAO Hangfang LI Chunxiao GONG Xianyi ZENG Xiaohui College of Information Science and Electronic Engineering Zhejiang University key laboratory ocean observation-imaging testbed of zhejiang province College of Mechanical Engineering Zhejiang University of Technology Hangzhou Applied Acoustics Research Institute

The ranges and radial velocities of targets are interesting parameters in the active sonar, which can＇t be observed directly but can only be estimated. Firstly, by making use of the delay-Doppler model of multi-targets in waveguide multipath environment, one finds that sample cross-ambiguity function is a two-dimensional（2D） convolution of the auto-ambiguity function of the transmitted signal with the generalized target reflectivity density, which is a 2D convolution of the spread function of channel with the reflectivity density as well. Secondly,from the perspective of information theory, an iterative deconvolution algorithm named R-L（Richardson-Lucy） is derived based on minimum Csiszar discrimination criterion. Finally, the blurs caused by both of the transmitted signal and channel are removed by 2D deconvolution of the expectation of sample cross-ambiguity function, 2D image and then parameters of time-delay and Doppler is estimated sequentially. Results of both numerical simulation and sea experimental data processing verify the feasibility and effectiveness of R-L deconvolution algorithm, which effectively improves the resolution and precision of the time delay and Doppler estimation, when compared to the classical match filtering and Wiener filtering.

关键词： waveguide reflectivity multipath discrimination iterative ambiguity convolution sonar Wiener filtering