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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

Low-resolution Kramers-Kronig detection system with error-feedback noise shaping

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Science China(Information Sciences) 2024年第5期67卷 259-269页

作者： Xiangyong DONG Zhenming YU Hongyu HUANG Kaixuan SUN Kun XU state key laboratory of Information Photonics and optical communications Beijing University of Posts and Telecommunications

In this paper, we investigated the effects of error-feedback noise shaping(EFNS) on a lowresolution Kramers-Kronig(KK) detection system for the first time. Both 16-ary quadrature amplitude modulation(16-QAM) and 64-ary quadrature amplitude modulation(64-QAM) were considered in the experiment. The carrier tone was added on the transmitter side using the virtual carrier-assisted single sideband(VCA-SSB) method to meet the minimum phase(MP) condition. Under the MP condition, KK detection only needs the intensity of the optical signal to be detected by one photodiode(PD) to retrieve the phase information. However, the virtual carrier tone increases the carrier-to-signal power ratio(CSPR), which results in a high peak-to-average power ratio(PAPR) at the transmitter, causing an increase in quantization noise. To mitigate quantization noise in the low-resolution KK detection system, EFNS was applied. The application of EFNS increased the optimal CSPR of the KK detection system and improved receiver sensitivity. Using a 4-bit DAC and the EFNS, 80 km transmission was achieved in the 60-Gbit/s 64-QAM KK detection system.

关键词： optical fiber communications Kramers-Kronig receiver error-feedback noise shaping quantization noise carrier-to-signal power ratio

Whispering-gallery-mode barcode-based broadband sub-femtometer-resolution spectroscopy with an electro-optic frequency comb

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advanced Photonics 2024年第1期6卷 115-125页

作者： Bingxin Xu Yangyang Wan Xinyu Fan Zuyuan He Shanghai Jiao Tong University State Key Laboratory of Advanced Optical Communication Systems and NetworksDepartment of Electronic EngineeringShanghaiChina Max-Planck Institute of Quantum Optics Hans-Kopfermann-Straûe 185748 GarchingGermany

Spectroscopy is the basic tool for studying molecular physics and realizing biochemical ***,it is challenging to realize sub-femtometer resolution spectroscopy over broad *** and high-resolution spectroscopy with calibrated optical frequency is demonstrated by bridging the fields of speckle pattern and electro-optic frequency comb.A wavemeter based on a whispering-gallery-mode barcode is proposed to link the frequencies of a probe continuous-wave laser and an ultrastable *** ultrafine electro-optic comb lines are generated from the probe laser to record spectrum of sample with sub-femtometer *** bandwidth is a thousandfold broader than comb bandwidth,by sequentially tuning the probe laser while its wavelength is *** approach fully exploits the advantages of two fields to realize 0.8-fm resolution with a fiber laser and 80-nm bandwidth with an external cavity diode *** spectroscopic measurements of an ultrahigh Q-factor cavity and gas molecular absorption are experimentally *** compact system,predominantly constituted by few-gigahertz electronics and telecommunication components,shows enormous potential for practical spectroscopic applications.

关键词： frequency comb reconstructive wavemeter spectroscopy

Butler matrix enabled multi-beam optical phased array for two-dimensional beam-steering and ranging

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Photonics Research 2024年第5期12卷 912-920页

作者： ZUOYU ZHOU WEIHAN XU CHUXIN LIU RUIYANG XU CHEN ZHU XINHANG LI LIANGJUN LU JIANPING CHEN LINJIE ZHOU state key laboratory of advanced optical communication Systems and Networks Shanghai Key Laboratory of Navigation and Location ServicesShanghai Institute for Advanced Communication and Data ScienceDepartment of Electronic EngineeringShanghai Jiao Tong UniversityShanghai 200240China SJTU-Pinghu Institute of Intelligent Optoelectronics Pinghu 314200China state Grid Sichuan Electric Power Company Chengdu Xinjin Power Supply Branch Xinjin 611430China

Based on the wavelength transparency of the Butler matrix(BM)beamforming network,we demonstrate a multibeam optical phased array(MOPA)with an emitting aperture composed of grating couplers at a 1.55μm pitch for wavelength-assisted two-dimensional *** device is capable of simultaneous multi-beam operation in a field of view(FOV)of 60°×8°in the phased-array scanning axis and the wavelength-tuning scanning axis,*** typical beam divergence is about 4°on both *** multiple linearly chirped lasers,multibeam frequency-modulated continuous wave(FMCW)ranging is realized with an average ranging error of 4 cm.A C-shaped target is imaged for proof-of-concept 2D scanning and ranging.

关键词： optical tuning beam

Extreme single-excitation subradiance from two-band Bloch oscillations in atomic arrays

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Photonics Research 2024年第3期12卷 571-580页

作者： LUOJIA WANG DA-WEI WANG LUQI YUAN YAPING YANG XIANFENG CHEN state key laboratory of advanced optical communication Systems and Networks School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Interdisciplinary Center for Quantum Information and state key laboratory of Modern optical Instrumentation Zhejiang Province Key Laboratory of Quantum Technology and Deviceand School of PhysicsZhejiang UniversityHangzhou 310027China MOE key laboratory of advanced Micro-Structured Materials School of Physics Science and EngineeringTongji UniversityShanghai 200092China Shanghai Research Center for Quantum Sciences Shanghai 201315China Collaborative Innovation Center of Light Manipulations and Applications Shandong Normal UniversityJinan 250358China

Atomic arrays provide an important quantum optical platform with photon-mediated dipole–dipole interactions that can be engineered to realize key applications in quantum information processing.A major obstacle for such applications is the fast decay of the excited *** controlling two-band Bloch oscillations of single excitation in an atomic array under an external magnetic field,here we show that exotic subradiance can be realized and maintained with orders of magnitude longer than the spontaneous decay time in atomic arrays with the finite *** key finding is to show a way for preventing the wavepacket of excited states scattering into the dissipative zone inside the free space light cone,which therefore leads to the excitation staying at a subradiant state for an extremely long decay *** show that such operation can be achieved by introducing a spatially linear potential from the external magnetic field in the atomic arrays and then manipulating interconnected two-band Bloch oscillations along opposite *** results also point out the possibility of controllable switching between superradiant and subradiant states,which leads to potential applications in quantum storage.

关键词： excitation Bloch decay

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

An isolated symmetrical 2T2R cell enabling high precision and high density for RRAM-based in-memory computing

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Science China(Information Sciences) 2024年第5期67卷 287-294页

作者： Yaotian LING Zongwei WANG Yuhang YANG Lin BAO Shengyu BAO Qishen WANG Yimao CAI Ru HUANG School of Integrated Circuits Beijing Advanced Innovation Center for Integrated Circuits Peking University state key laboratory of Information Photonics and optical communications Beijing University of Posts and Telecommunications

In-memory computing(IMC), leveraging emerging memories, holds significant promise in overcoming memory limitations and improving energy efficiency. However, the prevailing IMC array structure based on serially connected transistors and memory cells(1T1R/2T2R), along with the signed weight mapping scheme, can lead to asymmetrical weight sensing issues(AWS) due to electrical asymmetry within the1T1R/2T2R structure, particularly in highly scaled cells where the transistor's resistance becomes significant. In this paper, we propose and fabricate an electrically symmetric memory cell based on a physically isolated 2T2R structure for IMC. This design aims to enhance the precision and density of RRAM-based IMC arrays. The 2T2R cells are manufactured using the back-end-of-line(BEOL) process of a commercial40 nm technology platform. The feasibility of this design is verified through measured and simulated results,showcasing its capability to address the issue of AWS. Compared to conventional 2T2R cells, this design achieves a considerably smaller transistor footprint without compromising accuracy, while also improving integration density by 42.2%. These innovative memory cell advancements have the potential to further advance high-energy-efficient IMC technology.

关键词： RRAM 2T2R multi-level storage weight asymmetry in-memory computing

Enriched photosensitizer for deep-seated-tumor photodynamic therapy

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Photonics Research 2024年第5期12卷 1024-1035页

作者： HONGRUI SHAN XUEQIAN WANG QIHENG WEI HAILANG DAI XIANFENG CHEN state key laboratory on Fiber Optic Local Area communication Networks and advanced optical communication Systems Department of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China state key laboratory of Metal Matrix Composites Shanghai Key Laboratory for Molecular Engineering of Chiral DrugsSchool of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center of Light Manipulations and Applications Shandong Normal UniversityJinan 250358China

Photodynamic therapy(PDT)is an innovative approach that utilizes photochemical reactions for non-invasive disease *** PDT is limited by the low penetration depth of visible light required for ***,we employed upconversion nanoparticles(UCNPs)to extend the activation wavelength of photosensitizers into the infrared range,enabling a treatment depth of over 10 ***,we also used the abundant amino groups of branched polyethyleneimine(PEI)with spatial structure to enhance the loading capacity of protoporphyrin(PPIX),and we ultimately improved skin tumor clearance ***,we achieved tumor-specific treatment by utilizing folic acid(FA)targeting and active enrichment of *** to cellular experimental results,we demonstrated the remarkable reactive oxygen species generation capability of the material and ultra-low dark ***,we investigated the apoptosis mechanism and demonstrated that the synthesized nanoparticle stimulates the up-regulation of apoptosis-associated proteins Bax/Bcl-2 and Cyto *** in vivo experiments involving intravenous injection in mouse tails,we investigated the anticancer efficacy of the nanoparticle,confirming its excellent PDT *** research provides a promising avenue for future non-invasive treatment of deep-seated tumors,offering a method for the treatment and management of specific cancers.

关键词： treatment utilize utilizing

Tailoring electron vortex beams with customizable intensity patterns by electron diffraction holography

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Opto-Electronic Advances 2024年第2期7卷 14-21页

作者： Pengcheng Huo Ruixuan Yu Mingze Liu Hui Zhang Yan-qing Lu Ting Xu National laboratory of Solid-state Microstructures and Collaborative Innovation Center of advanced Microstructures Nanjing UniversityNanjing 210093China College of Engineering and Applied Sciences Key Laboratory of Intelligent Optical Sensing and Manipulation and Jiangsu Key Laboratory of Artificial Functional MaterialsNanjing UniversityNanjing 210093China

An electron vortex beam(EVB) carrying orbital angular momentum(OAM) plays a key role in a series of fundamental scientific researches, such as chiral energy-loss spectroscopy and magnetic dichroism spectroscopy. So far, almost all the experimentally created EVBs manifest isotropic doughnut intensity patterns. Here, based on the correlation between local divergence angle of electron beam and phase gradient along azimuthal direction, we show that free electrons can be tailored to EVBs with customizable intensity patterns independent of the carried OAM. As proof-of-concept, by using computer generated hologram and designing phase masks to shape the incident free electrons in the transmission electron microscope, three structured EVBs carrying identical OAM are tailored to exhibit completely different intensity patterns. Furthermore, through the modal decomposition, we quantitatively investigate their OAM spectral distributions and reveal that structured EVBs present a superposition of a series of different eigenstates induced by the locally varied geometries. These results not only generalize the concept of EVB, but also demonstrate an extra highly controllable degree of freedom for electron beam manipulation in addition to OAM.

关键词： electron vortex beam orbital angular momentum diffraction holography