Robust free-space optical frequency transfer in time-varying link distances conditions

Future inter-satellite clock comparison on high orbit will require optical time and frequency transmission technology between moving objects.Here,we demonstrate robust optical frequency transmission under the condition of variable link distance.This variable link is accomplished by the relative motion of a single telescope fixed on the experimental platform to a corner-cube reflector(CCR)installed on a sliding guide.Two acousto–optic modulators with different frequencies are used to separate forward signal from backward signal.With active phase noise suppression,when the CCR moves back and forth at a constant velocity of 20 cm/s and an acceleration of 20 cm/s^(2),we achieve the best frequency stability of 1.9×10^(-16) at 1 s and 7.9×10^(-19) at 1000 s indoors.This work paves the way for future studying optical frequency transfer between ultra-high-orbit satellites.

Four-stage cascaded variable optical attenuator with large attenuation range for quantum key distribution

A four-stage cascaded variable optical attenuator(VOA)with a large attenuation range is presented.The VOA is based on a Mach–Zehnder interferometer(MZI)and fabricated in a silica-based planar lightwave circuit(PLC)platform.The thermo-optic effect is used to achieve intensity modulation.The measured maximum attenuation of the four-stage cascaded VOA is 88.38 d B.The chip is also tested in a quantum key distribution(QKD)system to generate signal and decoy states.The mean photon number after attenuation of the four-stage cascaded VOA is less than 0.1,which can meet the requirement of QKD.

FeatureMatching Combining Variable Velocity Model with Reverse Optical Flow

The ORB-SLAM2 based on the constant velocity model is difficult to determine the search window of the reprojection of map points when the objects are in variable velocity motion,which leads to a false matching,with an inaccurate pose estimation or failed tracking.To address the challenge above,a new method of feature point matching is proposed in this paper,which combines the variable velocity model with the reverse optical flow method.First,the constant velocity model is extended to a new variable velocity model,and the expanded variable velocity model is used to provide the initial pixel shifting for the reverse optical flow method.Then the search range of feature points is accurately determined according to the results of the reverse optical flow method,thereby improving the accuracy and reliability of feature matching,with strengthened interframe tracking effects.Finally,we tested on TUM data set based on the RGB-D camera.Experimental results show that this method can reduce the probability of tracking failure and improve localization accuracy on SLAM(Simultaneous Localization and Mapping)systems.Compared with the traditional ORB-SLAM2,the test error of this method on each sequence in the TUM data set is significantly reduced,and the root mean square error is only 63.8%of the original system under the optimal condition.

The mid-infrared variability of the SDSS optical quasars

Based on the Seventh Data Release(DR7) quasar catalog from the Sloan Digital Sky Survey,we investigate the variability of optical quasars in W1,W2,W3 and W4 bands of the Wide-field Infrared Survey Explorer(WISE) and the Near-Earth Object Wide-field Infrared Survey Explorer(NEOWISE).Adopting the structure function(SF) method,we calculate the SF(δt = 1 yr) which shows no obvious correlations with the bolometric luminosity,the black hole mass and the Eddington ratio.The ensemble SFs in W1 and W2 bands show that the SF slopes are steeper than those in previous studies which may be caused by different cadence and observational epoch number.We further investigate the relation of variability amplitude σmbetween mid-infrared band and optical band,but no obvious correlation is found.No correlation is found between W1–W2 and g-r color.We think that the mid-infrared emission of quasars may be smoothed out by the extended dust distribution,thus leading to no obvious correlation.For the radio-loud quasar sub-sample,we further analyze the relation between the variability amplitude in the mid-infrared band and the radio luminosity at 6 cm,but no obvious correlations are found,which indicate the mid-infrared emission contributed from the synchrotron radiation of the relativistic jet is very weak.

Low power consumption 4-channel variable optical attenuator array based on planar lightwave circuit technique

The power consumption of a variable optical attenuator（VOA） array based on a silica planar lightwave circuit was investigated. The thermal field profile of the device was optimized using the finite-element analysis. The simulation results showed that the power consumption reduces as the depth of the heat-insulating grooves is deeper, the up-cladding is thinner,the down-cladding is thicker, and the width of the cladding ridge is narrower. The materials component and thickness of the electrodes were also optimized to guarantee the driving voltage under 5 V. The power consumption was successfully reduced to as low as 155 mW at an attenuation of 30 dB in the experiment.

Inverse design and realization of an optical cavity-based displacement transducer with arbitrary responses

Optical cavity has long been critical for a variety of applications ranging from precise measurement to spectral analysis.A number of theories and methods have been successful in describing the optical response of a stratified optical cavity,while the inverse problem,especially the inverse design of a displacement sensitive cavity,remains a significant challenge due to the cost of computation and comprehensive performance requirements.This paper reports a novel inverse design methodology combining the characteristic matrix method,mixed-discrete variables optimization algorithm,and Monte Carlo method-based tolerance analysis.The material characteristics are indexed to enable the mixed-discrete variables optimization,which yields considerable speed and efficiency improvements.This method allows arbitrary response adjustment with technical feasibility and gives a glimpse into the analytical characterization of the optical response.Two entirely different light-displacement responses,including an asymmetric sawtooth-like response and a highly symmetric response,are dug out and experimentally achieved,which fully confirms the validity of the method.The compact Fabry-Perot cavities have a good balance between performance and feasibility,making them promising candidates for displacement transducers.More importantly,the proposed inverse design paves the way for a universal design of optical cavities,or even nanophotonic devices.

The 650-nm variable optical attenuator based on polymer/silica hybrid waveguide

Visible light variable optical attenuators（VOA） are essential devices in the application of channel power regulation and equalization in wavelength-division multiplexing cross-connect nodes in plastic optical fiber（POF） transmission systems.In this paper, a polymer/silica hybrid waveguide thermo–optic attenuator based on multimode interference（MMI） coupler is designed and fabricated to operate at 650 nm. The single-mode transmission condition, MMI coupler, and transition taper dimensions are optimized through the beam propagation method. Thermal analysis based on material properties provides the optimized heater placement angle. The fabricated VOA presents an attenuation of 26.5 dB with a 21-mW electrical input power at 650 nm. The rise time and fall time are 51.99 and 192 μs, respectively. The time–stability measurement results prove its working reliability.

Optical Test of Local Hidden—Variable Model

An inequality is deduced from local realism and a supplementary assumption. This inequality defines an experiment that can be actually performed with the present technology to test local hidden-variable models, and it is violated by quantum mechanics with a factor 1.92, while it can be simplified into a form where just two measurements are required.

Fresnel Equations Derived Using a Non-Local Hidden-Variable Particle Theory

Problem: The Fresnel equations describe the proportions of reflected and transmitted light from a surface, and are conventionally derived from wave theory continuum mechanics. Particle-based derivations of the Fresnel equations appear not to exist. Approach: The objective of this work was to derive the basic optical laws from first principles from a particle basis. The particle model used was the Cordus theory, a type of non-local hidden-variable (NLHV) theory that predicts specific substructures to the photon and other particles. Findings: The theory explains the origin of the orthogonal electrostatic and magnetic fields, and re-derives the refraction and reflection laws including Snell’s law and critical angle, and the Fresnel equations for s and p-polarisation. These formulations are identical to those produced by electromagnetic wave theory. Contribution: The work provides a comprehensive derivation and physical explanation of the basic optical laws, which appears not to have previously been shown from a particle basis. Implications: The primary implications are for suggesting routes for the theoretical advancement of fundamental physics. The Cordus NLHV particle theory explains optical phenomena, yet it also explains other physical phenomena including some otherwise only accessible through quantum mechanics (such as the electron spin g-factor) and general relativity (including the Lorentz and relativistic Doppler). It also provides solutions for phenomena of unknown causation, such as asymmetrical baryogenesis, unification of the interactions, and reasons for nuclide stability/instability. Consequently, the implication is that NLHV theories have the potential to represent a deeper physics that may underpin and unify quantum mechanics, general relativity, and wave theory.

ELECTRON OPTICS OF VARIABLE RECTANGULAR SHAPED BEAM LITHOGRAPHY SYSTEM D J-2

The electron optical column for the variable rectangular-shaped beam lithographysystem DJ-2 is described,with emphasis on the analysis of the optical configuration and theshaping deflection compensation.In this column the variable spot shaping is performed with aminimum number of lenses by a more reasonable optical scheme.A high-sensitivity electrostaticshaping deflector with sequential parallel-plates is implemented for high-speed spot shaping.With a precise linear and rotational approach,the spot current density,the edge resolution aswell as the position of spot origin remain unchanged when the spot size varies.Experiments showthat the spot current density of over 0.4 A/cm^2 is obtained with a tungsten hairpin cathode,andthe edge resolution is better than 0.2μm within a 2×2 mm^2 field size.

Correlated Radio-Optical Variations on Intraday Timescales

Correlated radio-optical variations on intraday timescales have been observed （e.g. in BLO 0716＋714） and such radio intraday variability is suggested to have an intrinsic origin. Recently, multi-wavelength observations, simultaneous at radio, mm-submm, optical and hard X-rays, of 0716＋714, show that during a period of intraday/interday variations at radio and mm wavelengths, the apparent brightness temperature of the source exceeded the Compton-limit （-10^12 K） by 2-4 orders of magnitude, but no Compton catastrophe （or no high luminosity of inverse-Compton radiation） was detected. It is also found that the intraday/interday variations at mm-submm wavelengths are consistent with the evolutionary behavior of a standard synchrotron source and for the intraday/interday variations at centimeter wavelengths opacity effects can play a significant role, which is consistent with the interpretation suggested previously by Qian et al. Thus the apparent high brightness temperatures may probably be explained in terms of Doppler boosting effects due to bulk relativistic motion of the source. We will argue a scenario to simulate the correlations between the radio and optical variations on intraday timescales observed in BLO 0716＋714 in terms of a relativistic shock propagating through a jet with a dual structure.

Optical Gain Coefficient Measurements for 1-(4’-(Diphenylamino)-[1,1’-biphenyl]-4-yl)ethanone

In this study, the optical gain coefficient due to spontaneous emission for the conjugated compound 1-(4’-(diphenylamino)-[1,1’-biphenyl]-4-yl)ethanone (DBE) in two solvents, Tetrahydrofuran (THF) and Dichloromethane (DCM) was investigated using the variable stripe length method. The solutions were placed in 10 mm cuvettes and pumped optically with N2 laser (337 nm) with pulse duration of 1.2 ns and repetition rate of 10 Hz. A maximum net gain of 12 cm−1 for the compound in THF, and 7 cm−1 for the compound in DCM were recorded at the input energy of 162 μJ. The fluorescence quantum yields (∅f) of the compound were determined at the excitation wavelength of 337 nm using coumarin as a standard. The values of (∅f) for the samples in DCM and THF solvents were found to be 0.68 and 0.61, respectively. The high values of quantum yields suggest the possibility of using this material as an active media for lasing and for LED.

Finite-size analysis of eight-state continuous-variable quantum key distribution with the linear optics cloning machine

We propose a method to improve the secret key rate of an eight-state continuous-variable quantum key distribution（CVQKD） by using a linear optics cloning machine（LOCM）. In the proposed scheme, an LOCM is exploited to compensate for the imperfections of Bob＇s apparatus, so that the generated secret key rate of the eight-state protocol could be well enhanced. We investigate the security of our proposed protocol in a finite-size scenario so as to further approach the practical value of a secret key rate. Numeric simulation shows that the LOCM with reasonable tuning gain λ and transmittance τcan effectively improve the secret key rate of eight-state CVQKD in both an asymptotic limit and a finite-size regime.Furthermore, we obtain the tightest bound of the secure distance by taking the finite-size effect into account, which is more practical than that obtained in the asymptotic limit.

变光阑长波红外连续变焦光学系统设计

非制冷长波连续变焦光学系统由于相对孔径大导致小型化和无热化设计困难,本文采用可变光阑约束物镜尺寸压缩系统总长,实现长波640×512非制冷连续变焦光学系统轻小型化设计。通过材料合理配置及主动补偿实现5片透镜的8.5×连续变焦光学系统消热设计。该系统F#恒定1.2、工作波段为8~12μm、视场变焦范围为30°×24°~3.5°×2.8°、系统总长187.5 mm,该连续变焦光学系统重量轻、总长短、透过率高、在-40℃~+60℃温度范围全视场成像质量良好。

基于长度可变密钥的光学图像加密方法

为提升光学图像加密效果,设计了一种基于长度可变密钥的光学图像加密方法。基于混沌方程构成混沌序列均匀化普适算法,运用该算法生成均匀化伪随机序列,以此作为长度可变密钥,经空间光调制器调制后,转换此类密钥为伪随机相位掩模(PRPM),运用两个转换后PRPM双重随机相位编码初始光学图像,并结合变形分数傅里叶变换(AFrFT),相位转换编码后光学图像,获得加密光学图像,完成光学图像加密。实验结果显示,该方法可针对不同光学图像生成敏感性与唯一性密钥,实现不同光学图像的加密处理,加密效果显著,加密光学图像的像素频数分布均匀,且解密后光学图像与初始光学图像几乎一致,整体加解密效果理想,可有效保障光学图像的安全性,而且本方法可以在最短3 s的时间内完成光学图像的加密和解密,加解密效率更高,综合效果更佳。

基于可调光焦度器件的变焦内窥物镜光学设计

针对内镜外科手术中局部病灶图像不易获得的问题,提出一种基于可调光焦度器件的光学变焦内窥物镜光学设计系统.该系统基于Gauss括号法和内窥物镜变焦原理,推导分析可调光焦度器件的变焦内窥镜的一阶光学控制方程.应用一阶变焦光学理论的解析解和光学设计软件ZEMAX,对内窥镜3个典型变焦位置进行优化设计和成像评价,分析其光学成像能力.结果表明,基于可调光焦度器件的变焦内窥物镜对人体内壁组织变焦放大后具有辨别能力.该光学系统具有无组件移动、响应频率快和体积构造小等优点,可提高内窥镜治疗技术在外科治疗诊断的准确率.

基于改进谱线增强的光电编码器γ辐射噪声滤波算法研究

针对核辐射环境下光电编码器因受γ辐射总剂量效应影响而导致输出信号质量劣化的问题,提出了一种兼顾精度和效率的改进谱线增强算法(Improved Adaptive Line Enhancer Method,IALEM)。该算法引入Softsign函数建立误差与步长之间的非线性关系,通过在步长更新公式中引入前一时刻步长值,达到收敛速度快且稳态误差小的目的。分别在算法收敛速度、稳态误差、低信噪比输入、计算量4个方面与同类算法进行比较。结果表明,该算法在拥有较低计算量的同时,其收敛速度更快、稳态误差更小,并且对于低信噪比信号具有更好的滤波效果。最后,在光电编码器上对本文所提算法进行了现场可编程门阵列(Field Programmable Gate Array,FPGA)硬件实现;并在60Co γ辐射环境中对算法的滤波效果进行了实验测试。实验结果表明:所提出的算法可有效滤除光电编码器因γ辐射产生的噪声,提高光电编码器输出信号的质量。

杨氏模量实验测量方法的改进

介绍了梁弯曲法测量杨氏模量的实验方法,并在该方法基础上采用LVDT电压位移传感器去测钢尺弯曲形变的同时,增加了利用光杠杆进行读数的方法,对两种测量方法测得的实验数据进行比对,得到利用LVDT电压位移传感器测量数据的方法有实验数据的波动小、精确度高,并且实验装置更加简易,操作更加简单,读取数据直接等优点.

定日镜场在额定输出功率条件下的光学效率优化

为推动“双碳”目标实现,以光线追迹为核心,建立了定日镜平均输出热功率优化模型.首先,确定输出热功率是关于光学效率等参数的函数,通过给出阴影遮挡效率、集热器截断效率等参数的计算方法,提出了定日镜场输出热功率的计算方案.其次,提出定日镜场输出热功率的优化方案.针对定日镜规格相同的情况,提出“吸收塔选址策略”约束吸收塔的位置,提出“分区域同心圆规划策略”完成定日镜的排布,建立了定日镜输出热功率优化模型,并采用变步长搜索法完成最佳参数的求解.最后,针对定日镜规格不同的情况,提出“定日镜规格分区域规划策略”,并结合二分法和变步长搜索法完成最佳参数的求解.

基于GMM的幅度相位联合编码CVQKD安全性分析

为了提高离散调制连续变量量子密钥分发协议性能,采用幅度相移键控(APSK)联合调制格式方法,在接收端采用高斯混合模型分类算法识别量子态来提升系统的性能。将密钥传输系统分为状态学习和状态预测两个阶段,在状态学习阶段基于高斯混合模型的分类器对已知类别的量子态进行训练,学习不同类别量子态的幅度相位分布情况;在状态预测阶段则采用最小欧氏距离计算出待测量子态属于每个类别的后验概率,从而判定待测量子态的类别,并通过参数估计、反向协调和保密增强生成最终密钥。结果表明,在反向协调和集体攻击下128-APSK离散调制连续变量量子密钥分发协议能够有效生成安全密钥,当安全码率为10-6 bit/symbol时,传输距离可接近60 km。该研究为进一步提高离散调制连续变量量子密钥分发协议的系统性能提供了参考。