Experimental study of the time-resolved reflectivity of chromium film

The transient time-resolved reflectivity of chromium film is studied by femtosecond pump-probe technique with a 70-fs laser. Experimental results show that the reflectivity change increases with the power of the pump laser. The fast decrease of the reflectivity occurs between 0-200 fs which is mainly due to the electron-electron interaction. Subsequencely, the slower recovery of the reflectivity between 200-900 fs is mainly due to the electron-phonon coupling process. The reflectivity after 900 fs rises little to a near-constant value for the thermal equilibrium of the system. The experimental results can be explained properly with numerical simulation of the two-temperature model. It is helpful for understanding of the electron ultrafast dynamics in chromium film.     

olc型双折射滤波器离轴消光比的研究

提出了一种 ˇSolc型双折射滤波器的离轴消光比的一般性计算方法 ,利用所得结果模拟出了 ˇSolc型双折射滤波器的锥光干涉图以及发散光积分消光比与波长和发散角的关系曲线 ,实验结果证实了理论推算的合理性。此外本方法也适用于计算各种类型双折射滤波器的离轴消光比。     

基于空间-时间耦合的飞秒激光脉冲测量理论

现有的飞秒脉冲测量理论是建立在简化的脉冲模型基础上,即只对脉冲的时间特性进行测量,不考虑其空间特性.在实际中脉冲的空间特性和时间特性是相互依赖的,即使在自由空间传播的飞秒脉冲它的时间和空间特性之间也发生着相互的耦合作用.文中提出了飞秒激光脉冲测量理论中的时间-空间耦合脉冲模型.考虑到时间和空间之间的耦合作用,飞秒脉冲模型除了包含时间参量之外,还包含空间参量,即脉冲电场的表达式由E(t)变为E(x,y,z,t),给出了时间-空间耦合模型下的脉冲再现迭代算法.这一理论对飞秒脉冲的测量有重要的指导意义.     

Modal analysis of the Oth order nulled phase masks

A simple modal analysis （MA） method to explain the diffraction process of 0th order nulled phase mask is presented. In MA, multiple reflections of the grating modes at grating interfaces are considered by introducing equivalent Fresnel coefficients. Analytical expressions of the diffraction efficiencies and modal guidelines for the 0th order hulled phase grating design are also presented. The phase mask structure, which comprises a high-index contrast HfO2 grating and a fused-silica substrate, is optimized using rigorous coupled-wave analysis around the 800-nm wavelength, after which the modal guideline for cancellation of the 0th order in a phase mask is verified. The proposed MA method illustrates the inherent physical mechanism of multiple reflections of the grating modes in the diffraction process, which can help to analyze and design both low-contrast and high-contrast gratings.     

可实现任意形状的高效Zernike照明器

基于Ｚｅｒｎｉｋｅ的零级谱位相修正法能将单束激光以几乎是１００％的高效率转换成规则或不规则的振幅阵列，我们给出了位相和照明孔径空间压缩比之间的关系，并用一对位相板在实验上实现效率达８９％，３／４空间压缩比的３×３方形照明阵列。     

光色效应双掺杂(Fe,Mn):LiNbO3的光折变全息存储

采用双掺杂（Ｆｅ,Ｍｎ）：ＬｉＮｂＯ３晶体实现了光色效应光折变全息,实验上着重研究了不同氧化／还原状态晶体全息存储性能,结果表明,只有晶体具有较高的氧化程度才能实现全息的长期存储,与理论分析一致。     

深刻蚀光栅及其应用

深刻蚀光栅是一个新兴的学科方向,具有亚波长和深刻蚀舣重特征的微纳光子学元件,表现出一系列特有的光学效应.石英玻璃是一种优良的光学材料,具有热稳定性能好、透过率高、成本低等优点.基于石英玻璃制作深刻蚀光栅,是实现不同功能光子学器件的一种新技术途径,具有十分重要的应用前景.     

双倍密度光栅的飞秒压缩技术

飞秒激光技术是当前激光前沿领域的发展内容之一,飞秒脉冲的压缩手段更是其中重要的研究内容。在飞秒脉冲的压缩中,必须使用负的色散元件来补偿飞秒激光钛宝石晶体本身所具有的正的色散以实现压缩。现有的负色散补偿技术包括使用以下三种方式:高密度光栅对、棱镜对、啁啾镜。这三种补偿方式各有优缺点,其中,传统的高密度光栅对只能提供较大的色散量,往往用于飞秒脉冲大范围的展宽和压缩;啁啾镜提供的啁啾量较小,成本也太高;棱镜对的色散能力较小,需要较长的工作距离才能有足够的色散量,往往体积庞大,而且也太重。因此,发展一种新型的补偿方…     

Double-groove rectangular gratings for high-efficiency wideband vertical coupling in planar-integrated optical systems

A planar-integrated optical system(PIOS) represents powerful optical imaging and information processing techniques and is a potential candidate for the realization of a three-dimensional(3D) integrated optoelectronic intelligent system. Coupling the optical wave carrying information into a planar transparent substrate(typically fused silica) is an essential prerequisite for the realization of such a PIOS. Unlike conventional grating couplers for nano-waveguides on the silicon-on-insulator platfo...     

可实现任意形状的高效Zernike照明器

基于Zernike的零级谱位相修正法能将单束激光以几乎是100％的高效 率转换成规则或不规则的振幅阵列,我们给出了位相和照明孔径空间压缩比之间的关系, 并用一对位相板在实验上实现效率达89%, 3/4空间压缩比的3×3方形照明阵列。