基于EKF的水下LD通信精对准控制算法

高速激光通信中接收机与光斑中心很难处于精对准状态,导致水下光通信链路难以稳定建立.首先采用蒙特卡洛仿真统计法分析激光光子在海水中传输的接收光强分布规律,再通过实验对接收端的光斑图像进行采样分析,利用曲线拟合得到接收器位置与接收光强的关系.仿真与实验结果表明:光束经过25 m的水下传输,接收光强分布仍近似为高斯分布.采用非线性估计算法(扩展卡尔曼滤波)与基本状态控制反馈理论,根据接收光强度估计接收器当前位置与最大光强处的距离,通过反馈算法实现接收端与光斑中心的主动跟踪对准.算法仿真结果显示,接收端对准误差在2 mm以下,稳定后接收效率超过98%.     

Fano profile in a novel double cavity optomechanical system with harmonically bound mirrors

We investigate a double cavity optomechanical system generating single and double Fano resonance (multi-Fano). By altering a single parameter, the tunnelling rate g of the middle mirror, we are able to switch between single and double Fano line shapes. The first spectral line shape is stronger in the case of multi-Fano than in the case of single Fano. Also the behaviour of the steady state value of the displacement of the middle mirror, with respect to g, heavily influences the behaviour of double Fano lines in our scheme. This tunability along with using a single pump and signal/probe laser has an added advantage in situations where only low power consumption is available.     

Pressure of the fluctuating vacuum: Interpretation of the attractive and repulsive Casimir force

We calculate the Casimir force between two magnetodielectric slabs. The force expression is expressed in terms of parameters with which the repulsive effect is more transparent and convenient for numerical analysis. Finally, we propose a physical interpretation of the effect which clarifies the sign of force properly.     

手机虹膜识别镜头设计

随着近年来图像传感器的快速商用化以及生物识别算法的发展，虹膜识别功能得以应用于移动终端设备。获取虹膜图像是虹膜识别的关键一步，运用ZEMAX光学设计软件设计了一款适用于手机的虹膜识别镜头。该镜头采用豪威科技公司OmniVision_OV2281传感器，采用三片式非球面光学塑料设计，F数为2.3，全视场角为34°，在1/2奈奎斯特频率220 lp/mm处MTF值均大于0.39，且系统总长仅3 mm。根据ZEMAX像质评价方法以及公差分析结果可知，该镜头各项光学指标优良，具有像质好、体积小，质量轻、价格低、容易加工等特点。     

超越SNOM探针通光孔径尺寸的金属纳米间隙超分辨测量

采用电磁场有限元方法,数值模拟了孔径型扫描近场光学显微镜(aperture Scanning Near-field Optical Microscopy,a-SNOM)在照明模式下的工作过程.针对金偶极天线结构,改变天线长度和纳米间隙尺寸,计算了a-SNOM探针孔径的远场辐射速率随探针端面中心坐标变化的扫描曲线,实现了超越a-SNOM探针通光孔径尺寸的天线金属纳米间隙的超分辨测量,对于100nm通光孔径的探针,可分辨最小尺寸为10nm(0.016倍波长)的金属间隙.通过对比金属和介质偶极天线的a-SNOM探针远场辐射速率测量的计算结果,表明天线金属纳米间隙的超分辨测量的实现是由于金属间隙表面等离激元的激发.     

α-Mangostin exhibits antidepressant-like effects mediated by the modification of GABAergic,serotonergic and dopaminergic systems

Abstract

The present study explored the antidepressant-like activity of α-mangostin (α-MG) and the possible mechanism in this process in the tail suspension test (TST) in mice. The results revealed that α-MG (5?mg/kg, i.p.) exhibited markedly antidepressant-like activity, which could be reversed by pretreatment with haloperidol (a non-selective D₂ receptor antagonist), bicuculline (a competitive GABA antagonist), p-chlorophenylalanine (an inhibitor of 5-HT synthesis). Meanwhile, α-MG also effectively increased the brain DA, 5-HT and GABA levels in mice exposed to TST, indicating that the antidepressant-like effect of α-MG might be mediated by the GABAergic, serotonergic and dopaminergic systems.

     

Electrical switching effect in a photochromic molecule between two graphene electrodes

We propose a single-molecule electrical switches consisting of a photochromic dimethyldihydropyrene/cyclophanediene molecule sandwiched between two graphene electrodes and investigate the electronic transport by using density-functional theory and nonequilibrium Green's function methods. The “open” and “closed” isomers of the photochromic molecule are shown to have electrical switching behavior and negative differential resistance effect. Moreover, it is also found that the switching ratio between two different conductive states depends on the ambient temperature, and the device behaves as a stable electrical switch around room temperature, which is in agreement with a recent experimental study of another photochromic molecule diarylethene reported by Jia et al. (2016) [17].     

塞曼效应仿真实验平台

塞曼效应实验是学生了解原子具有磁矩和空间取向量子化现象的重要实验,至今塞曼效应仍是研究能级结构的重要方法之一.为了能够让学生更加清楚地了解塞曼效应实验的基本原理和操作规程,针对教学中的重点和难点,运用flash软件制作出塞曼效应仿真实验.该程序可全程高度仿真实验过程,具有界面友好、易于操作、无需安装等优点.为实验教学提供了一种新的辅助方式.     

基于数字全息的热透镜效应测量

提出一种数字全息定量测量半导体激光二极管侧面泵浦Nd∶YAG晶体热透镜效应的方法。CCD采集Nd∶YAG晶体在不同泵浦电流下的数字全息图,通过数值重建得到热透镜效应引起的相位分布及其变化过程。再由相位分布计算得到对应的热透镜焦距。实验结果表明,利用数字全息技术可以准确和有效测量热透镜效应及热透镜焦距。     

FFT动态相位重建算法的滤波窗影响分析

为了优化相位重建算法，针对波面干涉图的傅里叶频谱，分析了不同滤波窗口的分布特征和频谱响应，通过计算机仿真和实验测试，确定了FFT动态相位重建算法的最佳滤波窗口类型。其中处理仿真干涉图重建的波面与原始波面的波面峰谷值残差为0.008 5λ，波面均方根值残差为0.000 1λ；处理实验干涉图获得的波面与移相干涉测量法获得的波面峰谷值残差为0.009 3λ，波面均方根值残差为0.000 5λ。结果表明:选取Hamming窗进行滤波处理并重建的相位经拟合后得到的波面较参考波面的面形残差最小，相位重建精度优于0.01λ，可进一步应用于大口径光学元件的测量中。