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optical free induction decay emission carrying orbit angular momentum from ionic nitrogen enabled by multiple-photon resonance

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Chinese Optics Letters 2024年第6期22卷 177-181页

作者： Kailu Wang Haicheng Mei Jingsong Gao Liang Xu Hongbing Jiang Yi Liu Shanghai key laboratory of Modern optical system University of Shanghai for Science and TechnologyShanghai 200093China State key laboratory for Mesoscopic Physics School of PhysicsPeking UniversityBeijing 100871China CAS Center for Excellence in Ultra-intense Laser Science Shanghai 201800China

Coherent optical emission of free induction decay (FID) excited by the multiple-photon resonance has been recently observed in nitrogen ions produced by intense femtosecond laser *** we report that orbit angular momentum (OAM) of the pump laser pulses can be transferred to the much longer pulsed free induction decay emission with the OAM *** was found that when the pump laser frequency approaches the fraction of the 391.4 nm emission (ν_(0)/5),an FID emission is emitted whereas its topological charge was identified to be 5 times of the pump *** to the reduced laser intensity with a vortex pump compared to the conventional Gaussian beam,the resonant pump laser wavelength presents a redshift,and the FID signal is significantly weaker.

关键词： air lasing orbital angular momentum free induction decay femtosecond pulses photoionization

Atomic transport dynamics in crossed optical dipole trap

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Chinese Physics B 2024年第7期33卷 293-301页

作者：彭鹏张正熙樊耀塬殷国玲毛德凯陈徐宗熊炜周小计 State key laboratory of advanced optical Communication system and Network School of ElectronicsPeking UniversityBeijing 100871China Institute of Carbon-based Thin Film Electronics Peking UniversityTaiyuan 030012China State key laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-ElectronicsShanxi UniversityTaiyuan 030006China

We study the dynamical evolution of cold atoms in crossed optical dipole trap theoretically and experimentally. The atomic transport process is accompanied by two competitive kinds of physical mechanics, atomic loading and atomic *** loading process normally is negligible in the evaporative cooling experiment on the ground, while it is significant in preparation of ultra-cold atoms in the space station. Normally, the atomic loading process is much weaker than the atomic loss process, and the atomic number in the central region of the trap decreases monotonically, as reported in previous research. However, when the atomic loading process is comparable to the atomic loss process, the atomic number in the central region of the trap will initially increase to a maximum value and then slowly decrease, and we have observed the phenomenon first. The increase of atomic number in the central region of the trap shows the presence of the loading process, and this will be significant especially under microgravity conditions. We build a theoretical model to analyze the competitive relationship, which coincides with the experimental results well. Furthermore, we have also given the predicted evolutionary behaviors under different conditions. This research provides a solid foundation for further understanding of the atomic transport process in traps. The analysis of loading process is of significant importance for preparation of ultra-cold atoms in a crossed optical dipole trap under microgravity conditions.

关键词： cold atom crossed optical dipole trap transport process

Development of a toroidal soft x-ray imaging system and application for investigating three-dimensional plasma on J-TEXT

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Plasma Science and technology 2024年第3期26卷 94-99页

作者：赵传旭李建超张晓卿王能超丁永华杨州军江中和严伟李杨波毛飞越任正康 the J-TEXT Team International Joint Research laboratory of Magnetic Confinement Fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and TechnologySchool of Electrical and Electronic Engineering and School of PhysicsHuazhong University of Science and TechnologyWuhan 430074People's Republic of China Hubei key laboratory of optical Information and Pattern Recognition Wuhan Institute of TechnologyWuhan 430205People's Republic of China International Joint Research laboratory of Magnetic Confinement Fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and TechnologySchool of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074People's Republic of China

A toroidal soft x-ray imaging(T-SXRI)system has been developed to investigate threedimensional(3D)plasma physics on *** T-SXRI system consists of three sets of SXR *** sets are newly developed and located on the vacuum chamber wall at toroidal positionsφof 126.4°and 272.6°,respectively,while one set was established previously atφ=*** set of SXR arrays consists of three arrays viewing the plasma poloidally,and hence can be used separately to obtain SXR images via the tomographic *** sawtooth precursor oscillations are measured by T-SXRI,and the corresponding images of perturbative SXR signals are successfully reconstructed at these three toroidal positions,hence providing measurement of the 3D structure of precursor *** observed 3D structure is consistent with the helical structure of the m/n=1/1 *** experimental observation confirms that the T-SXRI system is able to observe 3D structures in the J-TEXT plasma.

关键词： SXR imaging J-TEXT tokamak three-dimensional measurement MHD

Design and Implementation of a Time Synchronization Method for UOWC Networks

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Journal of Communications and Information Networks 2024年第1期9卷 56-63页

作者： Weijie Liu Jingyi Zhang Nuo Huang Zhengyuan Xu CAS key laboratory of Wireless-optical Communications School of Information Science and TechnologyUniversity of Science and Technology of ChinaHefei 230027China

Underwater optical wireless communication (UOWC) technology facilitates high-speed data transmission among multiple nodes in underwater networks. Nevertheless, the absence of a common clock poses a challenge to achieving systematic and reliable access for multiple nodes within these networks. This paper presents a time synchronization method for UOWC networks to ensure the successful execution of the media access control (MAC) protocol. In this method, the node obtains timestamps by exchanging messages with the optical access point (OAP). Subsequently, the node calculates the clock drift relative to the OAP and the propagation time,ensuring that transmitted data packets can arrive approximately at the time specified by the OAP. To validate the effect of the proposed method, an experimental UOWC prototype, including the OAP and nodes, is implemented using field programmable gate array (FPGA). The experimental results demonstrate that the maximum difference between the actual arrival times of two data packets that are expected to reach the OAP simultaneously according to the MAC protocol meets the requirements of the quasi-synchronous code division multiple access (QS-CDMA) system, thereby substantiating the effectiveness of this synchronization method.

关键词： UOWC time synchronization MAC FPGA QS-CDMA

Radiation build-up and dissipation in Raman random fiber laser

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Science China(Information Sciences) 2024年第1期67卷 254-260页

作者： Shengtao LIN Zinan WANG Jiaojiao ZHANG Pan WANG Han WU Yifei QI key laboratory of optical Fiber Sensing and Communications University of Electronic Science and Technology of China College of Electronics and Information Engineering Sichuan University

Raman random fiber laser(RRFL) is a complex physical system that arises from the distributed Raman amplification and the intrinsic stochasticity of fiber *** analysis of the underlying lightwave kinetics at steady state has been the focus of considerable ***,the transient state,such as the RRFL build-up and dissipation,is particularly important for revealing the lightwave interaction ***,we investigate for the first time the RRFL dynamics at the transient state and track the RRFL temporal and spectral evolution theoretically and ***,with the contribution of random distributed feedback,RRFL build-up exhibits continuous Verhulst logistic growth curves without cavity-related features,which is significantly different from the step-like growth curve of conventional fiber ***,the radiation build-up duration is inversely related to the pump power,and the spectral evolution of the RRFL undergoes two phases,i.e.,from spectral density increase to spectral *** the steady state to the pump switch-off state,the RRFL output power dissipates immediately,and the remaining Stokes lightwave from the Rayleigh scattering will gradually disappear after one round *** work provides new insights into the transient dynamic features of the RRFL.

关键词： random fiber laser stimulated Raman scattering transient phenomenon nonlinear optics łinebreak biological growth dynamics

AWG-based large dynamic range fiber Bragg grating interrogation system

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Optoelectronics Letters 2024年第3期20卷 129-134页

作者： LI Shufeng YUAN Pei LI Ke LI Ting ZHU Lianqing key laboratory of the Ministry of Education for Optoelectronic Measurement technology and Instrument Beijing Information Science&Technology UniversityBeijing 100192China Beijing laboratory of optical Fiber Sensing and system Beijing Information Science&Technology UniversityBeijing 100016China

Arrayed waveguide gratings(AWGs) are extensively employed in fiber Bragg grating(FBG) interrogation systems due to their compact size, lightweight nature, and excellent interrogation performance. The resolution and total measurement range of AWG-based FBG interrogation systems are constrained by the output properties of AWG. We proposed an AWG-based large dynamic range interrogation system. The temperature dependence of AWG is exploited to achieve continuous interrogation. The test results show that the interrogation system has a dynamic range of 28.67 nm, an interrogation accuracy better than 25 pm, and a wavelength resolution of 6 pm.

关键词： fiber waveguide AWG

Gigahertz frequency hopping in an optical phase-locked loop for Raman lasers

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Chinese Physics B 2024年第2期33卷 60-65页

作者：毛德凯税鸿冕殷国玲彭鹏王春唯周小计 State key laboratory of advanced optical Communication system and Network School of ElectronicsPeking UniversityBeijing 100871China Institute of Carbon-based Thin Film Electronics Peking UniversityTaiyuan 030012China State key laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-ElectronicsShanxi UniversityTaiyuan 030006China Institute of advanced Functional Materials and Devices Shanxi UniversityTaiyuan 030031China

Raman lasers are essential in atomic physics,and the development of portable devices has posed requirements for time-division multiplexing of Raman *** demonstrate an innovative gigahertz frequency hopping approach of a slave Raman laser within an optical phase-locked loop(OPLL),which finds practical application in an atomic gravimeter,where the OPLL frequently switches between near-resonance lasers and significantly detuned Raman *** method merges the advantages of rapid and extensive frequency hopping with the OPLL’s inherent low phase noise,and exhibits a versatile range of applications in compact laser systems,promising advancements in portable instruments.

关键词： Raman lasers optical phase-locked loop frequency hopping

Simulation of random fiber Bragg grating array in polarization-maintaining fiber based on photonic localization effect

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Optoelectronics Letters 2024年第8期20卷 460-471页

作者： LI Zhihan HE Wei LI Shaode key laboratory of the Ministry of Education for Optoelectronic Measurement technology and Instrument Beijing Information Science and Technology UniversityBeijing 100192China Beijing laboratory of optical Fiber Sensing and system Beijing Information Science and Technology UniversityBeijing 100192China

Mid-infrared wavelength switchable and dual-wavelength random laser output has many potential applications.A polarization-maintaining random fiber Bragg grating(PMRFBG)array based on the photonic localization effect of longitudinal invariant transverse disorder in fiber structure is proposed,which can be used as random feedback of dual-wavelength and wavelength switchable output of random fiber laser(RFL).The random fiber Bragg grating(RFBG)array was designed on the panda-type polarization-maintaining fiber(PMF),and the two center wavelengths were 2151.60 nm and 2152.22 nm,*** RFBG array was designed on the bow tie-type PMF,and the two center wavelengths were obtained,which were 2153.08 nm and 2153.96 nm,*** RFBG array with a center wavelength of 2139.27 nm was designed on single-mode fiber(SMF).The length of individual fiber Bragg grating(FBG)and PMRFBG,the refractive index modulation depth,the number of cascaded gratings,and the distance between gratings have different effects on the full width at half maximum(FWHM)and reflectance of the RFBG and PMRFBG array,but not on the central wavelength,as obtained by simulation using the transmission matrix *** designed PMRFBG array provides theoretical support for the design of the feedback mechanism of RFL.

关键词： fiber polarization random

Silicon photonic integrated interrogator for fiber-optic distributed acoustic sensing

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Photonics Research 2024年第3期12卷 465-473页

作者： ZHICHENG JIN JIAGENG CHEN YANMING CHANG QINGWEN LIU ZUYUAN HE State key laboratory of advanced optical Communication system and Networks Department of Electronic EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Distributed acoustic sensing(DAS)technology has been a promising tool in various ***,the large size and relatively high cost of DAS equipment composed of discrete devices restrict its further popularization to some degree,and the photonic integration technology offers a potential *** this paper,we demonstrate an integrated interrogator for DAS on the silicon-on-insulator(SOI)*** design of the chip revolves around a Mach–Zehnder modulator(MZM)transmitter and a dual-quadrature and dualpolarization coherent *** integrated interrogator supports multiple DAS schemes,including the time-gated digital optical frequency domain reflectometry(TGD-OFDR),which is adopted for system performance evaluation.59■strain resolution in 12.1km sensing fiber with 1.14 m spatial resolution(SR)is ***,along 49.0 km sensing fiber,81■strain resolution with 3.78 m SR is *** results show that the integrated interrogator has comparable performance to the discrete DAS *** the best of our knowledge,this is the first dedicated on-chip DAS interrogator,which validates the effectiveness of the blend of photonics integration and DAS technology.

关键词： fiber polarization modulator