基于相位硅基液晶的光衍射演示实验

计算虚拟物体的衍射光场相位分布,然后加载到相位硅基液晶器件,利用平行光照射硅基液晶器件,可在光屏上看到虚拟物体的实像.根据相位硅基液晶的采样间隔,计算出虚拟物体的采样间隔,可预计虚拟物体大小.演示结果表明:处于菲涅尔衍射区域,衍射图像清晰,亮度高;而夫琅禾费衍射区的衍射图像虽然清晰,但比较暗淡.     

Multilayer Anisotropic Bi-periodic Diffraction Gratings

The formalism of Rokushima and Yamakita [J. Opt. Soc. Am. 73 (1983) 901] treating the diffraction on planar multilayered 1D anisotropic gratings is extended to the diffraction on anisotropic 2D multilayer grating structures bi-periodic in the plane parallel to the interfaces. In addition to the oblique incidence of plane waves, the case of normal incidence is also treated. The goal of the paper is to provide a basis for the formal analysis of 2D patterned multilayers with natural or induced anisotropies. For example, such structures are of interest in the design of new magnetic and magneto-optic devices. In view of the fact that the anisotropies have often a negligible effect on the energy distribution among diffracted modes with respect to the isotropic case the optical response is alternatively expressed in terms of the ellipsometric parameters of diffracted waves. The present analysis represents generalization of the problem of electromagnetic wave interactions in planar multilayers consisting of layers characterized by a general permittivity tensor treated by Yeh [J. Opt. Soc. Am. 69 (1979) 742].     

Far-field spectral intensity characteristics of a time-dependent gaussian pulse from a circular mask with a linear circular apertures array

The spectral characteristics of a time-dependent Gaussian pulse from a circular mask with a circular apertures array in the far field are theoretically investigated and presented with numerical results. A rigorous treatment, with the Fresnel diffraction integral, to the spectral changes of a time-dependent Gaussian-shaped pulse passing through a circular mask with a linear circular apertures array is given and some properties of the spectral intensity under different situations are provided. Also an accurate and concrete criteria judging the condition for the red shift, blue shift of spectral intensity distributions is obtained as well.     

表面具有光栅结构的sol-gel薄膜制备及衍射效率的研究

介绍了一种在 sol- gel薄膜表面形成光栅结构的方法。用扫描电子显微镜 (SEM)表征了薄膜的表面形貌 ,用原子力显微镜 (AFM)测量了光栅结构的深度。测试了这种结构表面的衍射特性 ,并对结果进行了分析     

高线密度X光透射光栅衍射效率

高线密度X光透射光栅是各种高分辨光栅摄谱仪的核心色散元件,为了获得较高的光谱分辨率,工作在2~5 keV能区的光谱仪需要使用5000 l/mm的X射线透射光栅。为了获得光栅的绝对衍射效率,采用同步辐射光在多个能点对5000 l/mm的X光透射光栅进行衍射效率实验标定,通过光栅相对衍射效率拟合获得了光栅结构参数,与光栅结构测量结果非常接近。然后,采用衍射效率的矩形栅线模型,计算得到了光栅的绝对衍射效率。     

二元矩形软X射线衍射光栅的标量区衍射理论

利用标量区衍射理论分析了正交二元矩形软Ｘ射线衍射光栅的光学特性，给出了理论设计的初步结果。     

调相光栅的正交相干相位检测

本文提出了一种解调调相光栅相位的新方法.将一幅相位调制光栅图输入计算机,通过正交相干相位解调算法处理,能够高精度、快速地获得光栅的相位分布.本文详细论述了正交相干相位解调原理,并给出实验系统和处理结果,最后与其他类似的相位解调方法进行了比较.     

运行双协议相位调制的量子密钥分发系统

基于差分编码方式提出一种改进方案.在Alice端用光纤马赫-曾德干涉仪产生双脉冲差分信号；在Bob端，用双法拉第反射式麦克尔逊干涉仪代替光纤马赫-曾德干涉仪，这种干涉仪能自动补偿环境引起的偏振抖动和光纤双折射引起的相位漂移，从而提高系统稳定性.双协议(即双脉冲差分协议联合BB84协议)的使用，增强了系统的安全性.该系统具有高效、安全、简洁、稳定等优点，在实验上实现了长期稳定的密钥分发和量子保密通信，误码率<5%，传输距离达80km.     

Tight focusing of phase modulated radially polarized hollow Gaussian beam using complex phase filter

We propose a new approach for generating multiple focal spot segment of sub wavelength size, by tight focusing of phase modulated radially polarized hollow Gaussian beam. The focusing properties are investigated theoretically by vector diffraction theory. We observed that focal segment with multiple focal spots structure separated with different axial distance can be generated by properly tuning the phase of the incident radially polarized hollow Gaussian (HGB) beam. Potential applications of this focal shaping technique are also discussed.     

Enhanced background rejection in thick tissue using focal modulation microscopy with quadrant apertures

Image formation in focal modulation microscopy using quadrant apertures (QFMM) is presented. The spatial resolution is discussed: compared with confocal microscopy, QFMM can simultaneously enhance the axial and transverse resolution. In contrast to focal modulation microscopy using D-shaped apertures (DFMM), QFMM can maintain x-y symmetry of spatial resolution, thus causing less confusion in imaging interpretation. The capability of background rejection is investigated, showing QFMM has the potential to increase imaging penetration depth. The signal level is also analyzed, indicating that the preferred detector pinhole radius is greater than for DFMM, resulting in a higher signal level.     

Diffraction from modulated structures I. Periodically modulated structures

The calculation of the diffraction amplitude from the periodical distribution of a finite number of zones extending in one direction is presented. The formulae for the diffraction amplitude of a single zone in terms of its structure parameters and for the diffraction amplitude of an array of zones embedded in the matrix for various types of modulation are given.     

用于PZT调制干涉仪的外触发式差动数字鉴相技术

基于相位测量的外差干涉系统以其信号处理方面的优势在光学计量领域得到了广泛的应用。介绍了采用机械调制方法的差动单频干涉系统的干涉信号小数级次的相位测量实现方法。针对机械调制干涉系统的信号有相位跃变点且周期不均匀的特点 ,提出了利用外触发信号对干涉信号进行整周期截取而后再鉴相的方法。研制了基于 FPGA的外触发式差动数字鉴相系统。实验测试表明 ,该鉴相系统在信号频率为 30 0 Hz～ 10 k Hz范围内达到的指标为 :示值稳定性优于± 0 .0 15°,极限偏差小于± 0 .0 7°     

相位调制高斯光束在强非局域非线性介质中的传输特性

利用(1+1)维Snyder-Mitchell模型和空间正弦相位调制的方法，讨论了如何控制高斯光束在平面波导中的传输问题，发现只要适当地选择调制参数就可得到稳定对称的三、五和六束子光束的共同传输，其独特全新的相互作用过程在光开关、编码器和分光器上有潜在的应用价值. 关键词： 强非局域非线性介质 空间相位调制 空间光孤子相互作用特性 光开关     

高斯光束在单轴晶体中的布拉格衍射特性

利用适当的坐标变换和黎曼方法建立了高斯光束在单轴晶体中布拉格衍射的严格的耦合波理论 ,获得了一组严格的耦合波方程和衍射效率计算公式 ,讨论了衍射效率随折射率调制量的关系以及波长选择性和角度选择性 ,同时分析了衍射效率对再现光宽度的要求。模拟计算表明 ,异常光与异常光 (ee)型布拉格衍射能够达到的最大衍射效率由记录时入射角决定 ,而且通过各参量的适当的选择 ,理论上ee型布拉格衍射能够在折射率调制量很低(如 8.2× 10 -5)的情况下获得接近 90 %的衍射效率。该理论模型为如何在较低折射率调制量下获得较高衍射效率提供了理论指导     

外加电场调制二维六角位相阵列光分束器的研究

本文建立了外加电场调制二维六角位相阵列光分束器的倒格矢理论模型, 利用数值模拟方法开展了阵列光分束器的理论研究, 对可调位相差阵列光分束器进行了分析, 得到了不同分数泰伯距离以及外加电场条件下的光强分布图. 实验设计与制备了铌酸锂二维六角位相阵列光分束器, 并对其进行了Talbot衍射光分束实验研究, 当外加电压为0.5 kV(电场为1 kV/mm)时, 观测到了Talbot衍射光分束现象, 随着外加调制电场的增大, 其衍射光分束图像越清晰, 该实验结果和理论研究结果相符.     

记录结构对体光栅各向异性衍射选择特性研究

以静态体光栅各向异性衍射理论分析模型为基础,将与体光栅厚度有关的记录光强调制度引入到各向异性耦合波方程中.利用耦合波理论分析了光折变晶体中体光栅的各向异性衍射性能,研究了在不同初始记录光强比的条件下,记录光入射角的改变对光折变体光栅各向异性布喇格衍射性能的影响.结果表明：记录光入射角和记录光初始光强比均对体光栅的各向异性衍射具有选择性;与此相比,记录光入射角和记录光初始光强比对于体光栅各向同性衍射不具备选择性.     

亚波长孔阵列的太赫兹波异常透射研究

利用太赫兹时域光谱（THz-TDS）系统,在5—300 K温区下测量了在厚度约200 nm的金属Nb薄膜刻蚀的亚波长圆孔阵列的异常THz波透射情况.实验结果表明,在03—2 THz波段,具有亚波长孔阵结构的金属Nb薄膜的异常透射现象波谱的峰位置与CST（computer simulation technology）软件仿真模拟的结果一致,峰值随温度降低有逐渐增强的趋势. 关键词： 亚波长孔阵列 THz时域光谱技术 异常透射     

Soliton generation from randomly modulated return-to-zero pulses

We consider return-to-zero (RZ) pulses with random phase modulation propagating in a nonlinear channel (modelled by the integrable nonlinear Schrödinger equation, NLSE). We suggest two different models for the phase fluctuations of the optical field: (i) Gaussian short-correlated fluctuations and (ii) generalized telegraph process. Using the rectangular-shaped pulse form we demonstrate that the presence of phase fluctuations of both types strongly influences the number of solitons generated in the channel. It is also shown that increasing the correlation time for the random phase fluctuations affects the coherent content of a pulse in a non-trivial way. The result obtained has potential consequences for all-optical processing and design of optical decision elements.     

Diffraction pattern of modulated structures described by Bessel functions

We performed detailed analysis of 1D modulated structure (MS) with harmonic modulation within the statistical approach. By applying two-mode Fourier transform, we were able to derive analytically the structure factor for MS with single harmonic modulation component. We confirmed in a very smooth way that ordinary Bessel functions of the first kind define envelopes tuning the intensities of the diffraction peaks. This applies not only to main reflections of the diffraction pattern but also to all satellites. In the second part, we discussed in details the similarities between harmonically modulated structures with multiple modulations and 1D model quasicrystal. The Fourier expansion of the nodes’ positions in the Fibonacci chain gives direct numerical definition of the atomic arrangement in MS. In that sense, we can define 1D quasicrystal as a MS with infinite number of harmonic modulations. We prove that characteristic measures (like v(u) relation typical for statistical approach and diffraction pattern) calculated for MS asymptotically approach their counterparts for 1D quasicrystal as large enough number of modulation terms is taken into account.     

速调管双间隙双耦合口输出结构

基于等效电路理论,提出了一种双间隙双耦合口输出结构的设计方法及计算双耦合口输出腔外观品质因数的方法。利用三维电磁场软件,设计了满足阻抗频率特性要求的双间隙单耦合口输出结构及前置腔和输出腔分别具有相同参数的双间隙双耦合口结构。然后,将两者的阻抗频率特性进行比较,通过微调整该输出腔与耦合槽的尺寸,可以得到与单耦合口输出结构一致的阻抗频率特性曲线。