Annealing effect on magnetic anisotropy in ultrathin（Ga,Mn）As

We investigated the effect of low temperature annealing on magnetic anisotropy in 7-nm ultrathin Ga0.94Mn0.06As devices by measuring the angle-dependent planar Hall resistance(PHR).Obvious hysteresis loops were observed during the magnetization reversal through the clockwise and counterclockwise rotations under low magnetic fields(below 1000 Gs,1 Gs = 10-4 T),which can be explained by competition between Zeeman energy and magnetic anisotropic energy.It is found that the uniaxial anisotropy is dominant in the whole measured ferromagnetic range for both the as-grown ultrathin Ga0.94Mn0.06As and the annealed one.The cubic anisotropy changes more than the uniaxial anisotropy in the measured temperature ranges after annealing.This gives a useful way to tune the magnetic anisotropy of ultrathin(Ga,Mn)As devices.     

可见-红外波段光全散射法颗粒粒径测量范围的研究

在光全散射法颗粒粒径测量中,采用独立模式算法在可见-红外波段对粒径测量范围进行了深入的研究。通过对多种R-R分布函数反演结果进行分析,比较,以确定光全散射法颗粒粒径测量范围。同时在消光系数计算中,采用修正的消光系数代替原始的消光系数,以便得到更准确的粒径测量范围。仿真计算结果表明,在可见-红外光谱区,相对折射率m=1.235时的粒径测量范围为0.05～18 μm。在此区域内测量粒径分布,反演结果与真值基本吻合。随着颗粒相对折射率、波长范围的变化,粒径测量范围也随之发生改变。采用限制最小二乘算法能够最大限度地克服随机噪声对测量结果的影响,使测量的精度和可靠性明显提高。对测量的消光值加入±1%随机噪声时,颗粒粒径分布的反演均能得到满意的结果。     

温度测量范围加倍的单微环传感器

本文提出了一种基于U形波导耦合单微环结构的新型SOI(绝缘体上硅)温度传感器.温度变化引起感温部位有效折射率和长度变化,导致传感器的输出光谱发生漂移.根据传输矩阵法和耦合模理论,设计了新型传感器模型,并且分析了感温部位不同时系统输出光谱特性.结果表明:当U形波导耦合单微环整体结构感温时,输出光谱无伪模,消光比达到31 dB,可作为最佳感温元件.相比于传统的双直波导耦合单微环结构,当U形波导的两个耦合点间的距离为微环周长的整数倍数时,FSR(自由光谱范围)可加倍至56 nm,灵敏度提高到89.2 pm/?C,测量范围为298—720 K,实现了SOI微环谐振器的高温测量.     

Highly sensitive digital optical sensor with large measurement range based on the dual-microring resonator with waveguide-coupled feedback

We propose a novel high-performance digital optical sensor based on the Mach-Zehnder interferential effect and the dual-microring resonators with the waveguide-coupled feedback. The simulation results show that the sensitivity of the sensor can be orders of magnitude higher than that of aconventional sensor, and high quality factor is not critical in it. Moreover, by optimizing the length of the feedback waveguide to be equal to the perimeter of the ring, the measurement range of the proposed sensor is twice as much as that of the conventional sensor in the weak coupling case.     

基于GRIN透镜微小角位移的测量技术研究

根据1/2波节自聚焦（GRIN）透镜中光的传输特性,提出了一种新颖的测量微小角位移的模型,通过对模型中光线传输和几何关系的理论分析,推导了待测角位移与光耦合效率之间的传递函数.针对模型对测量范围的限制,提出了一种可行的拓宽测量范围的方法.研究结果表明,该模型不但测量范围宽,而且测量准确度高,线性度好.     

Two-step pose estimation method based on five reference points

A two-step method for pose estimation based on five co-planar reference points is studied.In the first step, the pose of the object is estimated by a simple analytical solving process.The pixel coordinates of reference points on the image plane are extracted through image processing.Then,using affine invariants of the reference points with certain distances between each other,the coordinates of reference points in the camera coordinate system are solved.In the second step,the results obtained in the first step are used as initial values of an iterative solving process for gathering the exact solution.In such a solution,an unconstrained nonlinear optimization objective function is established through the objective functions produced by the depth estimation and the co-planarity of the five reference points to ensure the accuracy and convergence rate of the non-linear algorithm.The Levenberg-Marquardt optimization method is utilized to refine the initial values.The coordinates of the reference points in the camera coordinate system are obtained and transformed into the pose of the object.Experimental results show that the RMS of the azimuth angle reaches 0.076°in the measurement range of 0°-90°;the root mean square(RMS) of the pitch angle reaches 0.035°in the measurement range of 0°-60°:and the RMS of the roll angle reaches 0.036°in the measurement range of 0°-60°.     

Multi-hole plastic optical fiber force sensor based on femtosecond laser micromachining

We study the theoretical and experimental effects of hole quantity and inter–inter-hole spacing on insertion loss for using femtosecond laser to make bend-sensitive multi-hole plastic optical fiber(POF), and also analyze the mechanism of bending loss in multi-hole POF. A force sensor based on bending loss of the multi-hole POF is fabricated. The measurement ranges from 0 to 65 N, and the maximum output change exceeds 15.51 dB with good linearity and repeatability, and the sensitivity is 0.24 dB/N.     

等芯径等间距三光纤补偿式位移传感器的实验研究

介绍了补偿式光纤位移传感器的结构和原理,实验测量了等芯径等间距光纤位移传感器的输出特性和位移的关系. 结果表明:2根接收光纤各自的线性范围小,补偿后的光纤位移传感器不仅能改善测量的线性度,而且能在一定程度上放大传感器的线性测量范围. 补偿式光纤位移传感器采用等芯径等距离方式可以有效地消除光源输出强度波动、表面反射率不同和光纤传输损耗对输出特性的影响.     

基于遗传算法的差分吸收光谱反演算法及实验研究

传统差分吸收光谱法(DOAS)对大气痕量气体浓度可以实现准确、快速和在线测量,它对短光程、低浓度气体存在较大的测量误差.本文在传统DOAS算法的基础上,设计了基于遗传算法的DOAS算法,并对信噪比较低的实测光谱数据进行了浓度反演.研究结果表明,该算法在短光程下对低浓度气体具有较高的测量精度,与传统DOAS方法相结合可以获得较宽的动态测量范围.