软X射线多层膜反射式偏振光学元件设计

叙述了软X射线波段反射式多层膜起偏器和检偏器的设计原则和设计方法,计算了不同波段软X射线反射式多层膜起偏器和检偏器的性能,讨论了多层膜制作过程中,表界面误差(表面粗糙度和扩散)对起偏器和检偏器性能的影响,探讨了光谱分辨率对偏振元件测试过程的影响,这些设计、计算和分析为制作实用软X射线多层膜偏振光学元件提供了理论基础。     

8.0 nm反射式偏振膜的设计和制备

讨论了软X射线反射式偏振膜的设计原理和方法,利用设计软件模拟设计了8.0 nm处的Mo/B4C偏振膜.对影响多层膜性能的参量进行了详细的误差分析.利用磁控溅射镀膜机进行了偏振膜的制备研究,X射线小角衍射测量了多层膜的周期厚度,测量数据的拟合结果与设计值吻合很好.     

水窗波段反射式偏振光学元件的设计和制作

水窗波段是软X射线进行生物活细胞显微成像的最佳波段,因此对于水窗波段偏振光学元件的研究有着非常重要的意义。用菲涅耳公式计算出在水窗波段内不同材料组合对应不同波长的最大反射率,模拟分析了多层膜周期和表界面粗糙度对多层膜偏振光学元件性能的影响。用超高真空磁控溅射镀膜设备,制作出2．40nm、3．00nm和4．30nm波长处W／B4C多层膜偏振元件,并用X射线衍射仪对元件的周期厚度进行了测量,得到的测量结果与设计值偏差很小,可以进行实际应用。为水窗波段反射式偏振光学元件的研究提供了理论依据,同时也为相应偏振光学元件的制备确定了合适的工艺参量。     

宽波段波状多层膜结构偏振分束器的设计与优化

本文基于二维光子晶体波状多层膜结构,提出了叠加两种不同膜厚的周期膜堆来拓宽偏振分束器有效带宽的方法.采用粒子群优化算法,建立偏振分束特性的评价函数,优化结构和薄膜厚度等参数,获得了中心波长565 nm,带宽220 nm,平均消光比大于30 dB的宽波段偏振分束器.采用时域有限差分方法分析了膜层顶角的角度敏感性和波状结构的电场分布.结果表明,两个周期膜堆组合的结构解决了禁带不连续的情况,而粒子群优化算法的使用加快了结果收敛,有效地扩展了偏振分束带宽.     

利用等效层的消偏振宽带减反膜设计

分析了倾斜入射条件下导致光学薄膜产生偏振的原因,针对不同偏振态的等效导纳与等效相位进行了分析,并计算了对称膜层在45°入射条件下不同偏振态的等效折射率与等效相位厚度,采用等效层方法设计了光学性能良好的600～900 nm波段消偏振宽带减反膜。最后利用电子束蒸发技术制备了薄膜样品,样品的光谱性能完全能够满足使用要求。其中在600～900 nm波段范围内,平均反射率均小于1．38%,反射率的偏振度均低于0．89%。另外,通过对其理论及实验光学性能、角度敏感性、膜层厚度误差敏感性等方面的分析结果可知,对称膜层组合法是设计消除倾斜入射下宽带减反膜偏振效应的一种行之有效的方法。     

激光遥感偏振成像系统光学元件调整及误差分析

改进了利用双旋转波片方法进行偏振成像的实验装置,提出了通过一次测量获得目标偏振度和强度编码图像的方法.运用光强法对激光遥感偏振成像装置的光学元件进行调整,通过斯托克斯和穆勒矩阵在偏振光学元件中的应用,给出了相应光学元件的调整原理、方法及过程.分析了激光器中心波长变动、偏振片的角度误差和波片的相位延迟及角度误差对整个系统的影响.结果表明,由偏振片角度和波片角度误差造成的出射光斯托克斯误差较小,不超过0.001,可以忽略;由波片相位延迟不精确造成的误差在0.02左右,所以应采用延迟精度较高的波片;激光器中心波长变化的影响最大,不能忽略,必须加滤光片使接收光的中心波长控制在808nm;镀有铝膜望远镜对接收到的散射光偏振度影响较小,适于激光遥感偏振成像系统的应用.     

基于琼斯矩阵的FIR晶体光滤波器设计方法

FIR晶体光滤波器由夹在两个偏振片之间的N个厚度相同的晶片构成,设计过程中需要根据要求的频率响应求出各个晶体波片的光轴方向和输出端偏振片的通光方向.提出了一种基于琼斯矩阵的反向递推设计方法.FIR晶体光滤波器的琼斯矩阵是各个晶片以及偏振片琼斯矩阵的乘积,利用这一关系可以建立简单的反向递推关系,并计算出与输出偏振分量对应的正交偏振分量,通过迭代运算确定所有元件的角度参数.实例设计的结果与使用其它方法得到的结果一致,设计过程简单.     

一种反射式扭曲向列型液晶显示优化设计的新方法

基于扭曲向列型液晶的显示器件通过调制光波的偏振态实现显示的目的,因此光波的偏振状态在其中起了极为关键的作用.本文结合琼斯矩阵和表示光波偏振态的斯托克斯参量j-circle方法,提出了一种优化反射式扭曲向列型液晶显示器件的新方法.该方法与原有的空间参量方法不同的是采用了追踪光波在传播过程中偏振态变化的办法得到反射式液晶显示器件中各光学元件的参数.该方法简单直观并且可以对多个参数同时进行优化,实现了显示性能的最优化设计并得到了新的显示模式.     

基于梳状小波理论的颜色滤光片设计

渐变折射率薄膜因为消除了界面而克服了传统的分层介质膜的固有弊端。探讨了一种基于这种渐变膜系的设计方法。从小波理论及渐变折射率增透理论出发,以分层介质高反膜系为参照,给出了采用梳状(Rugate)滤光片设计不同类型颜色滤光片的设计原理,并以目前背投系统中使用的红、绿、蓝颜色滤光片为指标,理论设计出了具有优良光谱特性的红、绿、蓝颜色滤光片;对该设计结果进行了角度敏感性分析、偏振效应分析并与传统的反射膜叠加法得到的分层膜系进行比较,发现通过梳状滤光片理论设计的滤光片较传统的多层膜滤光片具有更小的角度敏感性和较小的偏振效应。     

基于模拟退火算法的宽角度X射线超反射镜设计研究

应用于硬X射线波段的宽带多层膜光学元件———宽角度X射线超反射镜的设计可以归结为一个连续变量的多维多极值的全局优化问题。缺少一种有效的全局优化方法是阻碍解决这一难题的一个关键。模拟退火算法是一种简单而且通用的全局优化算法。结合光学多层膜的设计原理提出了利用模拟退火算法来进行宽角度X射线超反射镜设计的新方法。结合已有的方法选择了W和C作为膜层的膜对材料,设计出Cu的Kα线处角度范围0.9°~1.1°反射率达到20%的宽角度X射线超反射镜。并在此基础上采用改进的自适应模拟退火算法实现了Cu的Kα线处宽角度X射线超反射镜的理想设计结果。设计结果表明了模拟退火算法在多层膜最优化设计领域的正确性和有效性。     

632.8nm波长质子交换光波导型偏振器的研究

在可见光域研制出钛扩散铌酸锂质子交换光波导偏振器，同时，给出波导偏振器参数测试装置。在理论上，利用物理光学和波导色散理论分析与计算了这种偏振器的消光比，分析了影响器件性能的各种因素，理论计算与实验结果符合良好。     

Fiber devices using polarization- maintaining fibers

Fiber devices using polarization-maintaining fibers called PANDA fibers are presented. They are polarization-maintaining couplers and polarization-splitting couplers, optical isolators and optical circulators, and multi/demultiplexers designed for 1.3 μm wavelength. Crosstalk of-32 dB and excess loss of 0.03 dB for the polarization-maintaining coupler, and polarization-splitting ratio of 17 dB and excess loss of 0.5 dB for the polarization-splitting coupler have been fabricated by a fusion-elongation method. A fiber polarizer with the extinction ratio of more than 40 dB has been presented by using the difference of bending loss between the orthogonal modes in the PANDA fibers. Multi/demultiplexer with narrow band-pass of 1.4 nm utilizing combination of PANDA fiber polarization dispersion and the polarization-splitting coupler has been realized. An optical isolator consisting of fiber polarizers and a spherical YIG with a lens function and an optical circulator consisting of polarizing-splitting couplers and spherical YIGs have been achieved.     

Fiber devices using polarization- maintaining fibers

Fiber devices using polarization-maintaining fibers called PANDA fibers are presented. They are polarization-maintaining couplers and polarization-splitting couplers, optical isolators and optical circulators, and multi/demultiplexers designed for 1.3 μm wavelength. Crosstalk of-32 dB and excess loss of 0.03 dB for the polarization-maintaining coupler, and polarization-splitting ratio of 17 dB and excess loss of 0.5 dB for the polarization-splitting coupler have been fabricated by a fusion-elongation method. A fiber polarizer with the extinction ratio of more than 40 dB has been presented by using the difference of bending loss between the orthogonal modes in the PANDA fibers. Multi/demultiplexer with narrow band-pass of 1.4 nm utilizing combination of PANDA fiber polarization dispersion and the polarization-splitting coupler has been realized. An optical isolator consisting of fiber polarizers and a spherical YIG with a lens function and an optical circulator consisting of polarizing-splitting couplers and spherical YIGs have been achieved.     

Subwavelength gratings fabricated on semiconductor substrates via E-beam lithography and lift-off method

We present results of the fabrication and measurements on reflective polarizers consisting of stacked bi-layer subwavelength metal gratings prepared on GaAs (100) substrates. These linear gratings were fabricated using electron-beam direct-writing lithography and the lift-off method with periods less than the wavelength of light used for measurements. At normal incidence, the polarizer reflects the light polarized perpendicular to the grating lines (transverse magnetic polarization, TM polarized) but absorbs parallel-polarized light (transverse electric polarization, TE polarized). By optimizing structural parameters, the polarization extinction ratio close to 20 has been experimentally achieved at wavelength of 650 nm.     

Hollow-core photonic bandgap fiber polarizer

Broadband, compact in-fiber polarizers were fabricated using a pulsed CO(2) laser to modify the air holes along one side of the hollow-core photonic bandgap fibers. The polarizers have lengths from 3 to 6 mm and exhibit a polarization extinction ratio of better than 20 dB over a wavelength range larger than 100 nm at approximately 1,550 nm.     

Performance of Polarizers and Coupler in an All Polarization Maintaining Fiber Interferometer

1 IntroductionThe fiber optic intefferometers are popular in the syStems of optical fiber sensors.The polarization maintaining fibers can improve the accuracy and stability of opticalfiber interferometers. An polarization maintaining fiber (Pine ) Michelsonnit.rferom.t..[l] can attain lOw-noise and high sensitivity Of COherent detection. Thequality of both the polarizers and the coupler in the systems can directly affect theoptical coherent signal to noise ratio (CSNR) of the interferomet…     

Performance of Polarizers and Coupler in an All Polarization Maintaining Fiber Interferometer

It is given mathematical models and analyze the performance of polarizers and coupler in an all polarization maintaining fiber (PMF) Michelson interferometer. The optical coherent signal to noise ratio (CSNR) of the interferometer is calculated by means of the Jones matrix with cross coupling matrix elements.     

Study of Polarizer Characteristics with a High-Power Terahertz Free Electron Laser

Though wire grid and strip polarizers are widely used for control of submillimeter radiation, both calculated and experimentally measured values of their transmission are often contradict one another. We have measured the transmission of wire and thin-film photolithographic polarizers at a wavelength of 0.13-mm using 100 W free electron laser radiation and compared the results with previous experiments and calculations. Using a thin-film photolithographic polarizer we showed that radiation of the Novosibirsk FEL after traveling through a 14-m beamline is plane-polarized with the degree of polarization better than 99.6%.     

双偏振结构保偏光纤偏振器的研制

提出了保偏光纤偏振器的一种串联结构,即双偏振结构,报道了研制的结果。并通过对单偏振结构和双偏振结构器件测试结果的比较,得出双偏振结构的保偏光纤偏振器可使器件达到高消光比,并且有稳定的温度特性。     

Single polarization transmission in pedestal-supported silicon waveguides

In this Letter, properties of a pedestal-supported silicon waveguide are investigated, showing that it supports single polarization transmission. The pedestal is fabricated easily through a wet-etching process on strip waveguides. Theoretical analysis shows that this property is due to the leakage of quasi-TM mode when the pedestal width is small. A polarization extinction ratio larger than 20 dB at 1550 nm is measured in the pedestal waveguide sample, demonstrating single polarization transmission property experimentally. Thanks to its large single polarization transmission bandwidth, robustness in fabrication tolerance, and simple fabrication process, pedestal waveguides will have potential applications as simple silicon-integrated polarizers.