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arXiv 2024年

作者： Yue, Shaohua Liu, Liang Di, Boya The State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Peking University Beijing100871 China The Department of Electronic and Information Engineering The Hong Kong Polytechnic University Hong Kong

Extremely large-scale multiple-input multiple-output (XL-MIMO) communications, enabled by numerous antenna elements integrated into large antenna surfaces, can provide increased effective degree of freedom (EDoF) to achieve high diversity gain. However, it remains an open problem that how the EDoF is influenced by the directional radiation pattern of antenna elements. In this work, empowered by the wavenumber-domain channel representation, we analyze the EDoF in a general case where the directivity of antennas, determined by the antenna structure and element spacing, is considered. Specifically, we first reveal the uneven distribution of directivity-aware wavenumber-domain coupling coefficients, i.e., channel gain towards different directions, in the isotropic Rayleigh fading channel. EDoF is then calculated based on such distribution of coupling coefficients. A numerical method is also provided to obtain coupling coefficients via electromagnetic full-wave simulations. Due to the influence of antenna directivity, how EDoF and ergodic channel capacity vary with the element spacing are explored via simulations for different antenna types. © 2024, CC BY.

关键词： Degrees of freedom (mechanics)

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Broadband and fabrication-tolerant 3-dB couplers with topological valley edge modes

arXiv

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arXiv 2024年

作者： Tang, Guo-Jing Chen, Xiao-Dong Sun, Lu Guo, Chao-Heng Li, Meng-Yu Tian, Zhong-Tao Chen, Hou-Hong Wang, Hong-Wei Sun, Qi-Yao Pan, Ying-Di He, Xin-Tao Su, Yi-Kai Dong, Jian-Wen School of Physics State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat-Sen University Guangzhou510275 China State Key Laboratory of Advanced Optical Communication Systems and Networks Department of Electronic Engineering Shanghai Jiao Tong University Shanghai200240 China

3-dB couplers, which are commonly used in photonic integrated circuits for on-chip information processing, precision measurement, and quantum computing, face challenges in achieving robust performance due to their limited 3-dB bandwidths and sensitivity to fabrication errors. To address this, we introduce topological physics to nanophotonics, developing a framework for topological 3-dB couplers. These couplers exhibit broad working wavelength range and robustness against fabrication dimensional errors. By leveraging valley-Hall topology and mirror symmetry, the photonic-crystal-slab couplers achieve ideal 3-dB splitting characterized by a wavelength-insensitive scattering matrix. Tolerance analysis confirms the superiority on broad bandwidth of 48 nm and robust splitting against dimensional errors of 20 nm. We further propose a topological interferometer for on-chip distance measurement, which also exhibits robustness against dimensional errors. This extension of topological principles to the fields of interferometers, may open up new possibilities for constructing robust wavelength division multiplexing, temperature-drift-insensitive sensing, and optical coherence tomography applications. Copyright © 2024, The Authors. All rights reserved.

关键词： Fabrication

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Narrow-Linewidth and Frequency-Agile FMCW Laser on the Si3N4-on-SOI Photonic Platform

Narrow-Linewidth and Frequency-Agile FMCW Laser on the Si3N4...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Chuxin Liu Xinhang Li Yuyao Guo Liangjun Lu Jianping Chen Linjie Zhou Department of Electronic Engineering State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Key Lab of Navigation and Location Services Shanghai Institute for Advanced Communication and Data Science Shanghai Jiao Tong University Shanghai China SJTU-Pinghu Institute of Intelligent Optoelectronics Pinghu China

We demonstrate a hybrid-integrated self-injection-locked laser on the Si 3 N 4 -on-SOI platform to generate FMCW signal with 9 kHz linewidth, 2 MHz repetition rate, and high linearity, supporting FMCW-LiDAR with refre... 详细信息

ISBN: (纸本)9798350369311

关键词： Linearity Electro-optical waveguides Photonics

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Amplitude-Invariant Phase Shifter Based on Carrier-Injection Mechanism for optical Phased Array

Amplitude-Invariant Phase Shifter Based on Carrier-Injection...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Qiqi Yuan Weihan Xu Shihuan Ran Yunhong Yang Liangjun Lu Jianping Chen Linjie Zhou Department of Electronic Engineering State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Key Lab of Navigation and Location Services Shanghai Institute for Advanced Communication and Data Science Shanghai Jiao Tong University Shanghai China SJTU-Pinghu Institute of Intelligent Optoelectronics Pinghu China

We present an amplitude-invariant phase shifter based on a PIN diode embedded in a Mach-Zehnder Interferometer for optical phased arrays. The dynamic power contrast is lower than 0.42 dB over a π phase shift.

ISBN: (纸本)9798350369311

关键词： Phased arrays Mach-Zehnder interferometers optical interferometry PIN photodiodes Phase shifters Lasers and electrooptics Semiconductor laser arrays Electro-optical waveguides optical arrays

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Continuous-Wave Mirrorless Lasing at 1.47m in Blue-Light Pumped Cs Vapor

Continuous-Wave Mirrorless Lasing at 1.47m in Blue-Light Pum...

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2021 Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium, EFTF/IFCS 2021 - Proceedings

作者： Shi, Tiantian Miao, Jianxiang Chen, Jingbiao Peking University State Key Laboratory of Advanced Optical Communication Systems And Networks Department of Electronics And Center For Quantum Information Technology Beijing100871 China

ISBN: (纸本)9781665439350

Population inversion on the 7S1/2 - 6P3/2 transition of cesium atoms is built by 455 nm diode laser pumping, and continuous-wave (cw) lasing is observed without the feedback on the gain medium from cavity mirrors. The stimulated emission at 1.47m infrared wavelength is restricted to a narrow angle along the direction of propagation of the pumping laser. Evidence of threshold-like characteristic is demonstrated in the cw mirrorless lasing dependence on pumping laser detuning, atomic density, and pumping light intensity. This compact structure can be used to generate mirrorless laser in a number of infrared wavelengths applied for the communication area. Moreover, it is expected to realize the narrow-linewidth optical frequency standard from an ultralow-finesse optical cavity. © 2021 IEEE.

关键词： Pumping (laser)

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Near-Far Field Three-Stage Beam Training for RIS-Assisted Wideband OFDM communications

Near-Far Field Three-Stage Beam Training for RIS-Assisted Wi...

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IEEE Conference on Wireless communications and Networking

作者： Zhichao Cheng Shupei Zhang Shu Fu Boya Di School of Electronics Engineering and Computer Science Peking University Beijing China State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Peking University Beijing China Department of Microelectronics and Communication Engineering Chongqing University Chongqing China

ISBN: (数字)9798350368369

ISBN: (纸本)9798350368376

Large-scale reconfigurable intelligent surfaces (RISs) have emerged as a promising technology for signal strength enhancement and coverage extension in 6G networks. However, as the antenna scale and the bandwidth increase, large-scale RIS-assisted wideband orthogonal frequency division multiplexing (OFDM) communication systems face new challenges due to the near-field range expansion and the beam split effect, complicating the acquisition of channel state information (CSI). To tackle these challenges, in this paper, we present a wideband beam training scheme by utilizing the beam split effect to bypass the CSI acquisition. Specifically, by analyzing the beam split effect in RIS-assisted OFDM communication systems, we propose a beam-split-aware codebook capable of covering both the near and far fields. The coverage of codewords in the proposed codebook is expanded benefiting from the beam split effect, leading to fewer codewords compared to conventional narrow-band codebooks. Utilizing such a codebook, a three-stage beam training mechanism is performed to obtain the optimal codeword with low time overhead, thereby facilitating the beamforming. Simulation results demonstrate that the proposed scheme outperforms existing codebook-based beam training schemes in terms of training overhead and sum rate in the hybrid near-far field.

关键词： Training Upper bound Array signal processing OFDM Simulation Reconfigurable intelligent surfaces Broadband antennas Wideband Faces Channel state information

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High Sensitivity Fiber Fabry Perot NH3 Sensor Based on PMMA Film

High Sensitivity Fiber Fabry Perot NH3 Sensor Based on PMMA ...

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International Conference on optical communications and networks (ICOCN)

作者： Feng Zhu Yingying He Yi Huang Chuanlu Deng Xiaoxiao Xu Zhengjie Xu Tingyun Wang Key Laboratory of Specialty Fiber Optics and Optical Access Networks Joint International Research Laboratory of Specialty Fiber Optics and Advanced Communication Shanghai Institute for Advanced Communication and Data Science Shanghai University Shanghai China State Grid Anhui electrical Power research Institute Hefei China

ISBN: (数字)9798350367652

ISBN: (纸本)9798350367669

Ammonia $(\text{NH}_{3})$ has been being widely used in medical and industrial applications. In this study, we demonstrated a fiber extrinsic Fabry-Pérot interferometer (EFPI) sensor, the interference cavity of which is configured by the end-face of single-mode fiber (SMF) and the polymethyl methacrylate (PMMA) film in a capillary. Based on high response characteristics of PMMA film for $\text{NH}_{3}$ , the sensor achieves a sensitivity of up to $500 pm/ppm$ for $\text{NH}_{3}$ concentration detection experimentally.

关键词： optical fiber sensors optical interferometry Ammonia Sensitivity Interference optical fiber networks Sensors

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Active Faraday optical Frequency Standard Based on Diffuse Laser Cooling of 87Rb atoms

Active Faraday Optical Frequency Standard Based on Diffuse L...

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European Frequency and Time Forum (EFTF)

作者： Xiaolei Guan Jia Zhang Xun Gao Tiantian Shi Jingbiao Chen State Key Laboratory of Advanced Optical Communication Systems and Networks Institute of Quantum Electronics School of Electronics Peking University Beijing China National Key Laboratory of Advanced Micro and Nano Manufacture Technology School of Integrated Circuits Peking University Beijing China Hefei National Laboratory Hefei China

ISBN: (数字)9798350354270

ISBN: (纸本)9798350354287

We proposed a scheme for realizing active Faraday optical frequency standards using diffuse laser cooling of alkali-metal atoms. A 1-m-long cold 87 Rb atomic cloud was prepared within a ϕ 2 cm × $l$ 1 m vacuum glass tube, featuring a maximum optical density of 4. By utilizing this setup to construct the Faraday anomalous dispersion optical filter, we are able to achieve an ultra-narrowband laser gain close to the natural linewidth of the atomic transition and corresponding to the hyperfine transition frequency. This ultra-narrowband laser gain can directly determine the output frequency of the active Faraday optical frequency standard operating in the “bad cavity” regime, significantly suppressing the cavity-pulling effect. Furthermore, due to the suppression of atomic collision and Doppler frequency shifts by the cold atoms, it is expected to further narrow the laser linewidth of the cold-atom-based active Faraday optical frequency standard to Hz level.

关键词： optical filters Atom optics Atom lasers Atomic beams Laser stability Atoms Laser cooling Laser transitions Standards Atomic clocks

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Near-Far Field Three-Stage Beam Training for RIS-Assisted Wideband OFDM communications

Near-Far Field Three-Stage Beam Training for RIS-Assisted Wi...

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2025 IEEE Wireless communications and Networking Conference, WCNC 2025

作者： Cheng, Zhichao Zhang, Shupei Fu, Shu Di, Boya School of Electronics Engineering and Computer Science Peking University Beijing China School of Electronics Peking University State Key Laboratory of Advanced Optical Communication Systems and Networks Beijing China Chongqing University Department of Microelectronics and Communication Engineering Chongqing China

ISBN: (纸本)9798350368369

关键词： Signaling

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3D Microwave Imaging as Point Cloud with Continous Normalizing Flows

3D Microwave Imaging as Point Cloud with Continous Normalizi...

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International Applied Computational Electromagnetics Society Symposium (ACES)

作者： Xueting Bi Lianlin Li State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Peking University Beijing China

Point cloud is a 3D representation with accurate location information, which can be applied to multi visual and graphic tasks. If the microwave can be imaged as a point cloud, the accurate position information of the target in the 3D solid space can be obtained, which is of great significance and great challenge. In this paper, a model of learning two-level distribution is designed for microwave imaging with point cloud as the target, that is, different kinds of targets are modeled into shape distribution, different individuals in the same kind are modeled into point distribution, and reversible continuous normalizing flow is used in each level. The visualization of experimental results shows that this method can produce impressive results.

关键词： Point cloud compression Visualization Solid modeling Three-dimensional displays Shape Gaussian distribution Microwave theory and techniques

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