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Simulation of nodal-line semimetal in amplitude-shaken optical lattices

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arXiv 2020年

作者： Zhou, Tanji Yu, Zhongcheng Li, Zhihan Chen, Xuzong Zhou, Xiaoji State Key Laboratory of Advanced Optical Communication Systems and Networks Department of Electronics Peking University Beijing100871 China School of Physics Peking University Beijing100871 China Collaborative Innovation Center of Extreme Optics Shanxi University Taiyuan Shanxi030006 China

With topologcial semimetal developing, semimetal with nodal-line ring comes into people’s vision as a powerful candidate for practical application of topological devices. We propose a method using ultracold atoms in two-dimensional amplitude-shaken bipartite hexagonal optical lattice to simulate nodal-line semimetal, which can be achieved in experiment by attaching one triangular optical lattice to a hexangonal optical lattice and periodically modulating the intensity and position of the triangular lattice. By amplitude shaking, a time-reversal-symmetry-unstable mode is introduced into the bipartite optical lattice, and then the nodal-line semimetal is gotten by adjusting the proportion of such mode and the trivial mode of hexagonal lattice. Through calculating the energy spectrum of effective Hamiltonian, the transformation from Dirac semimetal to nodal-line semimetal in pace with changing shaking parameters is observed. We also study the change of Berry curvature and Berry phase in the transformation, which provides guidance on measuring the transformation in experiment. By analyzing the symmetry of the system, the emergence of the time-reversal-symmetry-unstable mode is researched. This proposal provides a way to research the pure nodal-line semimetal without the influence of other bands, which may contribute to the study of those unique features of surface states and bulk states of nodal-line semimetal. Copyright © 2020, The Authors. All rights reserved.

关键词： optical lattices

Multi-Agent Genetic Algorithm for Sparse optical Phased Array Optimization

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Multi-Agent Genetic Algorithm for Sparse Optical Phased Arra...

Asia communications and Photonics Conference

作者： Chuxin Liu Weihan Xu Linjie Zhou Liangjun Lu Jianping Chen Shanghai Institute for Advanced Communication and Data Science Shanghai Key Lab of Navigation and Location Services State Key Laboratory of Advanced Optical Communication Systems and Networks Department of Electronic Engineering SJTU Shanghai China

We propose a multi-agent Genetic algorithm to suppress the peak sidelobe ratio (PSLR) in the OPA far-field diffraction pattern. The optimized 128-channel sparse array achieves beam-steering range of ±60° wit... 详细信息

ISBN: (纸本)9781943580705

关键词： Far field diffraction Free space optics Genetic algorithms optical coherence tomography Phased arrays Ptychography

Disaster Protection in Inter-DataCenter networks leveraging Cooperative Storage

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Disaster Protection in Inter-DataCenter Networks leveraging ...

GLOBECOM 2020 - 2020 IEEE Global communications Conference

作者： Yuanhao Liu Fen Zhou Cao Chen Zuqing Zhu Tao Shang Juan-Manuel Torres-Moreno CERI-SN IMT Lille Douai Institut Mines-Télécom University of Lille Villeneuve-d’ Ascq France State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Jiao Tong University China School of Information Science and Technology University of Science and Technology of China China State Key Laboratory of Integrated Service Networks School of Telecommunications Engineering Xidian University China CERI-LIA University of Avignon France

ISBN: (数字)9781728182988

ISBN: (纸本)9781728182995

Natural disasters have challenged the survivability of Elastic optical Inter-DataCenter networks (EO-DCNs), and it is urgent to establish efficient disaster protection schemes. In this paper, we investigate the disaster-resilient service provisioning problem leveraging cooperative storage system (CSS) and multipath routing. The studied problem involves data center (DC) assignment, content partition and placement, working/protection paths computation, as well as spectrum allocation. Our main objective is to jointly minimize the spectrum usage and maximal frequency slot index. Besides, we also expect to cut the content storage space. To this end, we first formulate the studied CSS-based protection problem as an integer linear program (ILP), and then propose a fast heuristic algorithm to improve the network scalability in large instances. Numerical simulations are conducted to compare the proposed schemes with the traditional protection strategy using entire content replication and single path routing. Simulation results demonstrate that the CSS-based protection scheme enables to cut up to 17.8% of the spectrum usage and half of the content storage space.

关键词： Cascading style sheets optical fiber networks Frequency selective surfaces Bandwidth Resource management Indexes Routing

Multi-node optical frequency dissemination with post automatic phase correction

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arXiv 2020年

作者： Hu, Liang Tian, Xueyang Wu, Guiling Kong, Mengya Shen, Jianguo Chen, Jianping State Key Laboratory of Advanced Optical Communication Systems and Networks Department of Electronic Engineering Shanghai Jiao Tong University Shanghai200240 China Shanghai Institute for Advanced Communication and Data Science Shanghai Jiao Tong University Shanghai200240 China the College of Physics and electronic information Engineering Zhejiang Normal University Jinhua321004 China

—We report a technique for coherence transfer of laser light through a fiber link, where the optical phase noise induced by environmental perturbation via the fiber link is compensated by remote users with passive phase noise correction, rather than at the input as is conventional. Neither phase discrimination nor active phase tracking is required due to the open-loop design, mitigating some technical problems such as the limited compensation speed and the finite compensation precision as conventional active phase noise cancellation. We theoretically analyze and experimentally demonstrate that the delay effect introduced residual fiber phase noise after noise compensation is a factor of 7 higher than the conventional techniques. Using this technique, we demonstrate the transfer laser light through a 145-km-long, lab-based spooled fiber. After being compensated, the relative frequency instability in terms of overlapping Allan deviation is 1.9 × 10−15 at 1s averaging time and scales down 5.3×10−19 at 10,000 s averaging time. The frequency uncertainty of the light after transferring through the fiber relative to that of the input light is (−0.36 ± 2.6) × 10−18. As the transmitted optical signal remains unaltered until it reaches the remote sites, it can be transmitted simultaneously to multiple remote sites on an arbitrarily complex fiber network, paving a way to develop a multi-node optical frequency dissemination system with post automatic phase noise correction for a number of end users. Copyright © 2020, The Authors. All rights reserved.

关键词： Natural frequencies

Fundamental limitations of Rayleigh backscattering noise on fiber-based multiple-access optical frequency transfer

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arXiv 2020年

作者： Hu, Liang Tian, Xueyang Wu, Guiling Shen, Jianguo Chen, Jianping State Key Laboratory of Advanced Optical Communication Systems and Networks Department of Electronic Engineering Shanghai Jiao Tong University Shanghai200240 China Shanghai Institute for Advanced Communication and Data Science Shanghai Jiao Tong University Shanghai200240 China College of Physics and Electronic Information Engineering Zhejiang Normal University Jinhua321004 China

Ultimate limits of performance for single-source-bidirectional architecture e.g., optical frequency transfer are set by delay fluctuations within the host material, e.g., optical fiber or atmospheric channel, which is dynamically induced. The most common manifestation of such phase disorder in the optical fiber is backscattering lights coming from Rayleigh backscattering and fresnel reflection, which is observed in nearly all single-source-bidirectional architectures and can lead to both irreversible coherence losses as well as undesirable interference coupling. While it has been shown that backscattering induced phase noise can be suppressed by adopting acoustic-optic-modulators (AOMs) at the local and remote sites to break the frequency symmetry in both directions. However, this issue can not be avoided for conventional fiber-optic multiple-access coherent optical phase dissemination in which the interference of the signal light with the Rayleigh backscattered light will probably destroy the coherence of the stabilized optical signal. We suppress the backscattering effect by locally breaking the frequency symmetry at the extraction point by inserting an additional AOM. Here, we theoretically analyze and experimentally demonstrate an add-drop one more AOM approach for suppressing the Rayleigh backscattering within the fiber link. Near-complete suppression of backscattering noise is experimentally confirmed through the measurementthe elimination of a common interference term of the signal light and the Rayleigh backscattered light. The results demonstrate that the Rayleigh backscattering light has a limited effect compared to the residual delay-limited fiber phase noise on the system’s performance. Our results also provide new evidence that it is possible to largely suppress Rayleigh and other backscattering noise within a long optical fiber link, where the accumulated phase noise could be large, by using frequency symmetry breaking at each access node to achieve ro

关键词： Natural frequencies

A Two-step Parameter Estimation Algorithm for Microwave Photonic Spectrum Awareness

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A Two-step Parameter Estimation Algorithm for Microwave Phot...

Signal, Information and Data Processing (ICSIDP), IEEE International Conference on

作者： Lu Chen Yesheng Gao Xingzhao Liu Zhicheng Wang State Key Laboratory of Advanced Optical Communication System and Networks Shanghai Jiao Tong University Shanghai China Shanghai Radio Equipment Research Institute Shanghai China

ISBN: (数字)9781728123455

ISBN: (纸本)9781728123462

Parameter estimation of wideband linear frequency modulation (LFM or chirp) signals is of significant importance in a wide range of areas such as radar, sonar and communications. However, estimation methods based on digital signal processing are limited by the calculation load. Thanks to the intrinsic advantages of large bandwidth, low transmission loss and immunity to electromagnetic interference of modern photonics, microwave photonic techniques are attractive for processing wideband signals. In this paper, a parameter estimation algorithm for the output signal of the photonics-based system is proposed. The algorithm consists of two steps. In the first stage, modified chirp Fourier transform is applied to estimate the parameters roughly. In the second stage, linear fitting and Rife algorithm are performed on the basis of the first step to obtain more accurate results. The simulation results demonstrate the efficacy of the proposed algorithm.

关键词：

870fs, 448kHz pulses from an all-PM Yb-doped fiber laser with a nonlinear amplifying loop mirror

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870fs, 448kHz pulses from an all-PM Yb-doped fiber laser wit...

Conference on Lasers and Electro-Optics/Pacific Rim, CLEOPR 2018

作者： Liu, Guanyu Wang, Aimin Zhang, Zhigang State Key Laboratory of Advanced Optical Communication System and Networks School of Electronics Engineering and Computer Science Peking University Beijing100871 China

We demonstrate a mode locked long all-polarization maintaining fiber laser with a nonlinear amplifying loop mirror. 870 fs pulse is obtained at the repetition rate of 448 kHz. © OSA 2018

ISBN: (纸本)9781943580453

We demonstrate a mode locked long all-polarization maintaining fiber laser with a nonlinear amplifying loop mirror. 870 fs pulse is obtained at the repetition rate of 448 kHz. © OSA 2018

关键词： Pulse repetition rate

Disentangled makeup transfer with generative adversarial network

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arXiv 2019年

作者： Zhang, Honglun Tian, Jidong Chen, Wenqing He, Hao Jin, Yaohui MoE Key Lab of Artificial Intelligence AI Institute Shanghai Jiao Tong University State Key Lab of Advanced Optical Communication System and Network

Facial makeup transfer is a widely-used technology that aims to transfer the makeup style from a reference face image to a non-makeup face. Existing literature leverage the adversarial loss so that the generated faces are of high quality and realistic as real ones, but are only able to produce fixed outputs. Inspired by recent advances in disentangled representation, in this paper we propose DMT (Disentangled Makeup Transfer), a unified generative adversarial network to achieve different scenarios of makeup transfer. Our model contains an identity encoder as well as a makeup encoder to disentangle the personal identity and the makeup style for arbitrary face images. Based on the outputs of the two encoders, a decoder is employed to reconstruct the original faces. We also apply a discriminator to distinguish real faces from fake ones. As a result, our model can not only transfer the makeup styles from one or more reference face images to a non-makeup face with controllable strength, but also produce various outputs with styles sampled from a prior distribution. Extensive experiments demonstrate that our model is superior to existing literature by generating high-quality results for different scenarios of makeup transfer. Copyright © 2019, The Authors. All rights reserved.

关键词： Generative adversarial networks

Experimental demonstration of multimode microresonator sensing by machine learning

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arXiv 2020年

作者： Lu, Jin Niu, Rui Wan, Shuai Dong, Chun-Hua Le, Zichun Qin, Yali Hu, Yingtian Hu, Weisheng Zou, Chang-Ling Ren, Hongliang College of Information Engineering Zhejiang University of Technology Hangzhou310023 China CAS Key Laboratory of Quantum Information University of Science and Technology of China Hefei230026 China College of Science Zhejiang University of Technology Hangzhou310023 China State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Jiao Tong University Shanghai200240 China

A multimode microcavity sensor based on a self-interference microring resonator is demonstrated experimentally. The proposed multimode sensing method is implemented by recording wide band transmission spectra that consist of multiple resonant modes. It is different from previous dissipative sensing scheme, which aims at measuring the transmission depth changes ofa single resonant mode in a microcavity. Here, by combining the dissipative sensing mechanism and the machine learning algorithm, the multimode sensing information extracted from a broadband spectrum can be efficiently fused to estimate the target parameter. The multimode sensing method is immune to laser frequency noises and robust against system imperfection, thus our work presents a great step towards practical applications of microcavity sensors outside the research *** voltage applied across the microheater on the chip was adjusted to bring its influence on transmittance through the thermo-optic effects. As a proof-of-principle experiment, the voltage was detected by the multimode sensing approach. The experimental results demonstrate that the limit of detection of the multimode sensing by the general regression neural network is reduced to 6.7% of that of single-mode sensing within a large measuring range. Copyright © 2020, The Authors. All rights reserved.

关键词： Research laboratories