Anomalous time-reversal symmetric non-Hermitian systems

The conditions for the emergence of the non-Hermitian skin effect, as a unique physical response of non-Hermitian systems, have now become one of the hot research topics. In this paper, we study the novel physical responses of nonHermitian systems with anomalous time-reversal symmetry, in both one dimension and two dimensions. Specifically, we focus on whether the systems will exhibit a non-Hermitian skin effect. We employ the theory of generalized Brillouin zone and also numerical methods to show that the anomalous time-reversal symmetry can prevent the skin effect in onedimensional non-Hermitian systems, but is unable to exert the same effectiveness in two-dimensional cases.

Topological Anderson insulator in two-dimensional non-Hermitian systems

We study the disorder-induced phase transition in two-dimensional non-Hermitian systems.First,the applicability of the noncommutative geometric method(NGM)in non-Hermitian systems is examined.By calculating the Chern number of two different systems(a square sample and a cylindrical one),the numerical results calculated by NGM are compared with the analytical one,and the phase boundary obtained by NGM is found to be in good agreement with the theoretical prediction.Then,we use NGM to investigate the evolution of the Chern number in non-Hermitian samples with the disorder effect.For the square sample,the stability of the non-Hermitian Chern insulator under disorder is confirmed.Significantly,we obtain a nontrivial topological phase induced by disorder.This phase is understood as the topological Anderson insulator in non-Hermitian systems.Finally,the disordered phase transition in the cylindrical sample is also investigated.The clean non-Hermitian cylindrical sample has three phases,and such samples show more phase transitions by varying the disorder strength:(1)the normal insulator phase to the gapless phase,(2)the normal insulator phase to the topological Anderson insulator phase,and(3)the gapless phase to the topological Anderson insulator phase.

Photon counting statistics of V-type three-level systems:The effects of the field fluctuations

We investigate the influence of the field fluctuations to the emission photons of V-type three-level systems.The emission intensity I and Mandel＇s Q parameter show stochastic resonance with respect to the pure dephasing constantγp.The amplitude fluctuation of the field causes these systems to lose their coherence.On the other hand,the amplitude fluctuation provides a new interference method for these systems.The quantum beats are shown in the orthogonal system.

Transmission-reflection decoupling of non-Hermitian photonic doping epsilon-near-zero media

We present a novel method to achieve the decoupling between the transmission and reflection waves of non-Hermitian doped epsilon-near-zero(ENZ)media by inserting a dielectric slit into the structure.Our method also allows for independent control over the amplitude and the phase of both the transmission and reflection waves through few dopants,enabling us to achieve various optical effects,such as perfect absorption,high-gain reflection without transmission,reflectionless high-gain transmission and reflectionless total transmission with different phases.By manipulating the permittivity of dopants with extremely low loss or gain,we can realize these effects in the same configuration.We also extend this principle to multi-port doped ENZ structures and design a highly reconfigurable and reflectionless signal distributor and generator that can split,amplify,decay and phase-shift the input signal in any desired way.Our method overcomes limitations of optical manipulation in doped ENZ caused by the interdependent nature of the transmission and reflection,and has potential applications in novel photonic devices.

PET image reconstruction with a system matrix containing point spread function derived from single photon incidence response

A point spread function（PSF） for the blurring component in positron emission tomography（PET） is studied. The PSF matrix is derived from the single photon incidence response function. A statistical iterative reconstruction（IR） method based on the system matrix containing the PSF is developed. More specifically, the gamma photon incidence upon a crystal array is simulated by Monte Carlo（MC） simulation, and then the single photon incidence response functions are calculated. Subsequently, the single photon incidence response functions are used to compute the coincidence blurring factor according to the physical process of PET coincidence detection. Through weighting the ordinary system matrix response by the coincidence blurring factors, the IR system matrix containing the PSF is finally established. By using this system matrix, the image is reconstructed by an ordered subset expectation maximization（OSEM） algorithm. The experimental results show that the proposed system matrix can substantially improve the image radial resolution, contrast,and noise property. Furthermore, the simulated single gamma-ray incidence response function depends only on the crystal configuration, so the method could be extended to any PET scanner with the same detector crystal configuration.

Photon counting statistics in single multi-level quantum system

We theoretically study the statistics of photon emission of single multi-level quantum system by employing the generating functions approach developed recently. The generalized decay constants are included in single multi-level quantum system with quasi-degenerated levels in this work although they are normally neglected in the absence of （quasi-）degeneracies in multi-level quantum system within the rotating wave approximation. The quantum beats, the line shapes and the Mandel＇s Q parameters, etc. are studied.

光储备池通感一体通信噪声抑制方案(封面文章·特邀)

通感一体技术可利用已大范围铺设的光纤网实现智能传感,具备智能识别、信息融合优势。在同波长通感共传信道中,通感信号串扰及光纤传输噪声严重影响通信信号质量,需提升发射功率来保证低误码率,但增大了非线性噪声和功耗。提出了基于光储备池计算神经网络的通感共传信道通信失真均衡方法,搭建了信道均衡仿真系统,实现了低发射功率下前向通信信号噪声均衡。周期线性调频光和56 Gb/s四电平脉冲幅度调制信号分别用于分布式瑞利散射传感和数据通信。仿真结果表明,在5~14 dBm入纤功率时,与未均衡信号相比该方法可提供高于3个数量级以上的误码率优化。此方法在短距离模块间15~24 km光纤传输和0.5~2.0 GHz带宽线性调频感测脉冲下均实现了2个数量级以上的误码率下降。依托光储备池计算芯片的低能耗和低延时优势,该方法可为进一步提升通感一体系统中噪声抑制能力提供理论支撑。

基于无人机集群的综合一体化告警自卫系统设计

现代战争中,无人机已经成为各大军事强国的重要武器装备之一,可被应用于侦察、目标探测、情报搜集、攻击等多种作战任务中,无人机集群作为无人机发展的新方向,具有作用范围大、灵活性强、战术使用多样化等优点,能够更好地完成在复杂战场环境下的各种任务,大大提高了作战效能。传统的机载告警自卫系统功能较为单一,且智能化程度不够高,极大地限制了载机的作战能力和任务执行能力,并不能满足无人机集群的应用设想。文中基于当前无人机集群的应用方式和环境,提出一种多功能综合一体化的告警自卫系统设计架构,在满足传统告警功能的基础上额外增加了智能化和侦察对抗一体化的功能,并在硬件模块上做了一定的优化调整,基本上可以满足无人机集群的应用规划和设想。

星载单光子激光雷达海洋噪声模型

星载单光子激光雷达以超高灵敏度和超高重频的优势,在海洋探测领域展现了广泛的应用前景。雷达系统中的单光子探测器件具有极高的灵敏度,可以探测光子量级的回波信号,同时也极易受太阳背景光噪声影响。由于背景噪声直接影响激光雷达的工作性能,还会对星上原始的数据量产生影响,在卫星系统设计阶段,对噪声强度的准确估计至关重要。本文综合考虑大气后向散射、水面反射及水体后向散射的贡献,建立了一个星载单光子激光雷达海洋噪声的估计模型。以全球首个对地观测星载激光雷达ATLAS为例,在输入系统参数和环境参数后,模型估计的噪声与ATLAS实测噪声误差在15%以内,证实了该噪声模型的正确性。

基于T型透镜排布的多频干涉系统设计及成像

为探究多频点采集对成像的影响,提出并搭建了一种T型透镜排布的多频干涉系统,该系统可以同时对二维光栅目标的多个空间频率进行采集。实验成功实现了二维光栅图像的重建,系统仿真得到的图像峰值信噪比(PSNR)为30.79 dB,实验重建图像PSNR为27.95 dB,重建图像的整体结构未发生改变。成像系统的设计及成像的过程也为该技术的实际工程应用提供了指导和方向。

高能同步辐射光源科学数据传输系统设计和实现

【目的】高能同步辐射光源HEPS(High Energy Photon Source)是我国第一台高能量同步辐射光源,预计2025年建成。HEPS建成后,首批投入使用的15条光束线站预计每天会产生200TB实验数据。为满足不同阶段对实验数据的读写需求,会对海量实验数据进行分级存储和长期备份。如何将这些数据在不同存储介质之间稳定和高效地传输是HEPS实验中需要解决的重要问题。【方法】HEPS科学数据传输系统设计了多源DAQ接口、任务调度、消息队列、集群传输、日志监控、配置管理和消息通知等功能模块。【结论】系统实现了海量数据在不同存储介质间的高效、可靠传输。【结果】系统现部署在北京同步辐射多个线站,用作HEPS数据传输的前期验证,运行稳定、效果良好,为科研人员和用户提供了良好的数据传输服务。

用于FBG解调的AWG芯片的设计、仿真与制备

设计、仿真并制备了一种用于光纤布拉格光栅(FBG)解调的阵列波导光栅(AWG)芯片。该芯片基于SOI衬底进行制备,并在AWG的输入/输出波导、阵列波导与平板波导之间采用双刻蚀结构进行优化。经仿真,该AWG的插入损耗为1.5 dB,串扰小于-20 dB,3 dB带宽为1.5 nm。优化后的AWG芯片采用深紫外光刻技术、电感耦合等离子体等技术制备。经测试,该AWG的插入损耗为3 dB,串扰小于-20 dB,3 dB带宽为2.3 nm。搭建了基于该AWG的解调系统,解调实验结果表明,该系统在0.8 nm范围内的解调精度可达11.26 pm,波长分辨率为6 pm。

基于超导单光子探测器的红外光学系统噪声分析和优化

高灵敏度的红外探测系统对于远距离探测有巨大的潜力,但光学系统内部的噪声会抑制探测系统的信噪比,从而降低探测灵敏度与探测距离.本文基于红外超导纳米线单光子探测器,设计了一个工作在中红外波段的光学系统,构建了红外光学系统自发辐射计算模型,理论分析了红外光学系统的信噪比和噪声特性.首次提出了利用高性能超导单光子探测器精确表征红外光学系统的微弱背景辐射光信号,为优化设计红外系统提供了依据.并且基于超导单光子探测器的光子计数能力,研究了光学系统的背景辐射对红外探测系统性能的影响,并优化了光学系统的性能.实验结果表明,超导单光子探测器对于分析红外光学系统具有较高的灵敏度,最小可分辨移动距离为2.74×10^(-2)mm,在黑体温度为100℃时,光子计数率提高了6.4×10^(4)cps(1 cps=1 cycle per second),光学系统的耦合效率提升了97%;在黑体温度为102℃时,光子计数率提高了9.1×10^(4)cps,光学系统的耦合效率提升了114%,降低了杂散辐射对探测系统的影响,同等条件下系统信噪比提升2.7倍,对于超导红外探测系统的应用研究具有重要意义.

Observation of topological rainbow in non-Hermitian systems

Topological photonic states have promising applications in slow light,photon sorting,and optical buffering.However,realizing such states in non-Hermitian systems has been challenging due to their complexity and elusive properties.In this work,we have experimentally realized a topological rainbow in non-Hermitian photonic crystals by controlling loss in the microwave frequency range for what we believe is the first time.We reveal that the lossy photonic crystal provides a reliable platform for the study of non-Hermitian photonics,and loss is also taken as a degree of freedom to modulate topological states,both theoretically and experimentally.This work opens a way for the construction of a nonHermitian photonic crystal platform,will greatly promote the development of topological photonic devices,and will lay a foundation for the real-world applications.

基于光电振荡器的变电站设备高精度温度监测系统

为有效监测变电站设备的实时温度,提出一种基于光电振荡器的高精度温度实时监测系统。首先,将温度信息映射到光电振荡器的振荡频率;然后利用现场可编程逻辑门阵列对温度参量进行实时解算,并通过4G模块将数据无线传输至终端,完成变电站设备温度的在线监测。通过实验验证了本系统对变电站设备温度实时监测的可行性和有效性。

基于单光子线性APD的信息提取算法研究

针对新型单光子线性APD器件获得信息维度多、灵敏度高的特点,提出了一种基于单光子线性APD的微弱回波信号距离信息提取算法。首先利用微弱信号的泊松分布特性对回波信号进行建模,随后对每纳秒内的回波光子数进行统计,利用与脉宽等宽的距离窗进行滑窗求和,将最大值位置作为信号脉冲接收时刻,进而反算距离信息。设计了跟踪前的目标搜索策略和稳定跟踪后的距离门匹配算法,有效降低了背景光干扰和计算资源消耗,在回波光子数分别为200、10、5个时分别获得了100、9993、9658的计算正确率。对单光子量级信号设计了脉冲积累算法,单个光子信号回波的计算正确率为995。同时对静止目标通过算法迭代实现了信噪比为0dB甚至负dB的信息提取,对003个光子信号回波探测的计算正确率为961。仿真结果表明该算法可以综合应用单光子线性APD的强度信息以及单光子灵敏度,实现了在极限灵敏域下的距离信息提取。

一种非接触式光学微腔液压测量系统

为满足在狭小腔室中测量液体压强的需求,设计了一种非接触式光学法布里珀罗微腔液压测量系统,其中,光学微腔采用双光子三维打印技术制备,膜结构尺寸仅为350μm,设计的膜厚分别为4μm和6μm。系统主要采用嵌入式设计与衍射光栅光谱模块互联,实时采集光学微腔干涉光谱信号,实现了高精度光谱动态解调。实验结果表明,室温(25℃)下,4μm膜厚的微腔液压灵敏度高达398 pm/kPa,系统分辨率可达35.5 Pa,重复性较好,有望用于生物医学眼压等应用场景。

TI-RADS分级联合SPECT诊断甲状腺良恶性结节的价值分析

目的:分析甲状腺影像报告和数据系统(Thyroid Imaging Reporting and Data System,TI-RADS)分级联合单光子发射计算机断层成像术(Single-photon Emission Computed Tomography,SPECT)对甲状腺良恶性结节的诊断价值.方法:选取2021年1月至2022年12月我院82例甲状腺结节患者,分析TI-RADS分级、SPECT诊断及联合诊断结果,并对甲状腺结节良恶性的诊断价值采用受试者工作特征(Receiver Operating Characteristic,ROC)曲线进行分析.结果:TI-RADS分级联合SPECT诊断结果中良、恶性结节分别为58个、24个.TI-RADS分级联合SPECT对甲状腺良恶性结节诊断的灵敏度、特异性、准确度高于TI-RADS分级和SPEC单独诊断(P<0.05).TI-RADS分级联合SPECT诊断甲状腺良恶性结节的曲线下面积(Area Underthe Curve,AUC)最大为0.849.结论:TI-RADS分级联合SPECT能够提高对甲状腺良恶性结节的诊断效能和准确率.

Lowering the energy consumption in silicon photonic devices and systems [Invited]

We review current silicon photonic devices and their performance in connection with energy consumption.Four critical issues are identified to lower energy consumption in devices and systems: reducing the influence of the thermo-optic effect, increasing the wall-plug efficiency of lasers on silicon, optimizing energy performance of modulators, and enhancing the sensitivity of photodetectors. Major conclusions are(1) Mach–Zehnder interferometer-based devices can achieve athermal performance without any extra energy consumption while microrings do not have an efficient passive athermal solution;(2) while direct bonded III–V-based Si lasers can meet system power requirement for now, hetero-epitaxial grown III–V quantum dot lasers are competitive and may be a better option for the future;(3) resonant modulators, especially coupling modulators, are promising for low-energy consumption operation even when the power to stabilize their operation is included;(4) benefiting from high sensitivity and low cost, Ge/Si avalanche photodiode is the most promising photodetector and can be used to effectively reduce the optical link power budget. These analyses and solutions will contribute to further lowering energy consumption to meet aggressive energy demands in future systems.

Cavity optomechanics： Manipulating photons and phonons towards the single-photon strong coupling

Cavity optomechanical systems provide powerful platforms to manipulate photons and phonons, open potential ap- plications for modern optical communications and precise measurements. With the refrigeration and ground-state cooling technologies, studies of cavity optomechanics are making significant progress towards the quantum regime including non- classical state preparation, quantum state tomography, quantum information processing, and future quantum internet. With further research, it is found that abundant physical phenomena and important applications in both classical and quan- tum regimes appeal as they have a strong optomechanical nonlinearity, which essentially depends on the single-photon optomechanical coupling strength. Thus, engineering the optomechanical interactions and improving the single-photon optomechanical coupling strength become very important subjects. In this article, we first review several mechanisms, theoretically proposed for enhancing optomechanical coupling. Then, we review the experimental progresses on enhancing optomechanical coupling by optimizing its structure and fabrication process. Finally, we review how to use novel structures and materials to enhance the optomechanical coupling strength. The manipulations of the photons and phonons at the level of strong optomechanical coupling are also summarized.