测量单模波导参数的新方法:导模和漏模的双偏振测量

本文提出测量单模波导参数的新方法.用棱镜耦合器测量两种偏振基导模和基漏模的模折射率,并由相应的四个模方程确定单模波导参数.其测量精度优于纯导模测量.用这种方法测量了单模玻璃波导参数,并对误差来源作了理论分析.     

各向异性聚合物薄膜参数的测量与计算

讨论了用单侧漏模法测量薄膜共振漏模的耦合角、计算漏模的有效折射率并由相应的模方程来确定各向异性聚合物薄膜折射率ｎ０、ｎｅ及厚度ｄ的方法。对ＰＴ－ＰＥＫ－ｃ（酞酸铅－聚醚醚酮）膜，测量与计算结果为：ｎｏ＝１．６５２５±０．００１４，ｎｅ＝１．６４３９±０．００１９，ｄ＝２．３３±０．３２μｍ。     

基于棱镜的椭偏法测量液体复折射率

通过引进等腰棱镜,利用椭偏测量技术实现了液体复折射率的精确测量.基于菲涅尔公式及椭偏测量原理,从理论上分析仪器测量得到的椭偏参数与棱镜-液体界面椭偏参数的关系,并讨论了测量液体折射率及吸收系数的精度.使用消光式椭偏仪,测量了水和印度墨水的复折射率,得到了样品的折射率、吸收系数随浓度变化的实验曲线,实验结果与参考文献基本一致.实验表明:棱镜椭圆偏振技术测量液体折射率及吸收系数的精度分别为0.000 4和0.000 3,适合于快速测量.     

基于多孔金膜的太赫兹导模共振生化传感特性仿真

仿真设计了一种高灵敏度太赫兹(THz)导模共振生化传感结构.该结构由硅棱镜、介质薄膜和多孔金膜组成,多孔金膜同时作为THz导波层和生化分子富集层,能够增强THz导模与生化分子间的相互作用,从而提高探测灵敏度.当采用棱镜全反射方法激励THz横电(TE)或横磁(TM)导模后,多孔金膜的吸收使得THz反射频谱出现尖锐的共振吸收峰,由此可确定THz导模的共振频率及其对液体折射率和生化分子吸附量的灵敏度.调节介质层的厚度和折射率可进一步提高上述THz传感结构的灵敏度和品质因数.在45°入射角下的仿真结果指出, TE和TM导模的共振频率随着液体折射率或生化分子吸附量的增大而线性变化,TM导模的折射率灵敏度可高达13.42 THz/RIU,品质因数达到167.70/RIU, TE导模对液体折射率的灵敏度小于TM导模,但对分子吸附量的灵敏度大于TM导模,究其原因是TE导模透出多孔金膜的消逝场比TM导模弱.     

液晶全漏导模透射率的实验研究

实验研究了由棱镜、折射率匹配液及扭曲排列和垂直排列向列相液晶盒构成的液晶全漏导模的透射率。随着施加在液晶盒上的电压不同,得到了依赖于角度变化的透射率（包括偏振保存和偏振转换）的实验曲线。这些曲线由液晶指向矢在液晶盒中的分布直接控制,由此可以证实液晶全漏导模透射率同样可以用来探索液晶盒内部的细微变化。     

方形容器测量液体折射率和色散率

介绍了一种利用激光测液体折射率的简易方法.通过测量光线穿过垂直棱镜角后发生全反射时的入射临界角,进而求出液体的折射率.再利用折射率与临界角的关系,结合科希经验公式求出液体色散率.     

棱镜耦合法测量掺杂波导模折射率中的误差分析

讨论了棱镜耦合法测量离子交换掺Er-Yb平面光波导中传播模式的模折射率实验中的误差与不确定度,模折射率误差由耦合棱镜折射率与底角及同步入射角误差决定，得出了测量模折射率不确定度的传递公式,作为实例．用Ag^＋-Na^＋离子交换技术,在285℃下交换15min．得到了Er-Yb共掺磷酸盐玻璃平面波导，给出了波导模折射率（@632．8nm）及不确定度。     

光波导技术同步测量棱镜及波导薄膜参数

依据全反射理论和棱镜耦合原理,实现了对棱镜折射率及波导薄膜材料折射率和厚度的同步测量。使用高准直半导体激光器激光入射到棱镜内部与波导膜的分界面上,逐步旋转棱镜或改变棱镜的入射角,得到棱镜耦合M线,曲线前面几组的波谷为波导模激发,在M线左侧收尾处有一个不完整波峰,其反射光强随入射角迅速衰减,为全反射时的临界点,由此可实现棱镜及波导薄膜参数的同步测量;用此法测量了棱镜耦合一体化平面波导棱镜的折射率和聚甲基丙烯酸甲酯(PMMA)聚合物波导薄膜的折射率和厚度。测量棱镜折射率精度为±1.9×10-4,波导薄膜折射率和厚度的精度分别为±6.2×10-4 μm和±1.6×10-2 μm。     

几何画板模拟阿贝折射仪测折射率

几何画板模拟阿贝折射仪测量液体折射率的过程,相对传统教学手段,更加科学直观并动态演示。通过修改棱镜折射率和待测液体折射率的参数,通过直观几何光学分析,得到为何阿贝折射仪必须满足棱镜折射率大于待测折射率。利用程序易修改特点研究,棱镜不同顶角和考虑色散现象的模拟结果,定量研究差别。     

三棱镜偏向角与棱镜顶角的关系

从几何光学理论系统地讨论了棱镜偏向角与顶角的关系,并由Matlab绘出棱镜顶角A与棱镜最小入射角、材料折射率n的关系曲线.结果表明,在测量三棱镜折射率及使用棱镜光谱仪时,对棱镜的顶角是有一定要求的.     

A proposed new experimental setup for determination of refractive indices of liquids by mode line measurements

A new experimental method is proposed for measuring the refractive indices of liquids based on mode line measurements. The experimental setup consists of a dielectric substrate in which a rectangular hollow is formed containing the concerned liquid. This is covered by a trapezium-shaped prism. The liquid, confined between both basin walls and the prism, forms a wavegude. Thus, the refractive index of the liquid can be determined by measuring the propagating modes in the structure. Using this technique, the refractive indices of liquids can be measured to an accuracy of the order of 1×10^-4.     

Absorption Measurement Using a Leaky Waveguide Mode

We propose an optical waveguide sensor using a leaky mode for absorption measurement of liquid samples. This sensor uses a single coupling prism. A cladding layer and a waveguide layer are directly deposited on the reflecting surface of the prism. The intensity of the internally reflected beam at an appropriate incident angle is very sensitive to the imaginary part of the sample attached to the surface of the waveguide layer. The sensitivity of this sensor is controlled by the thicknesses of both cladding and waveguide layers. We studied the performance of the sensor by numerical calculation.     

Measurement of thin film parameters using substrate excitation of leaky modes

Using substrate excitation achieved by prism coupling into the substrate, thin film leaky mode m-lines can be measured and the thickness and refractive index determined, without pressure applied to the film.     

LiNbO3质子交换波导及其退火效应

采用质子交换技术,以苯甲酸为交换源,实验研究X-切LiNbO₃质子交换平面波导及其退火效应。利用棱镜耦合器测出波导模折射率。采用费米函数,由模折射率确定出波导折射率分布随退火时间的变化关系,给出了分布参数和曲线.     

Study of optical parameters of two fluorinated isothiocyanato nematic liquid crystals exhibiting high birefringence

Optical studies have been carried out on two fluorinated isothiocyanato nematic liquid crystal (LC) compounds 4′-butylcyclohexyl-3, 5-difluoro-4-isothiocyanatobiphenyl and 4′-pentylcyclohexyl-3, 5-difluoro-4-isothiocynatobiphenyl. Transition temperatures of the two samples were confirmed using a polarizing microscope. The two LC compounds were found to exhibit fairly high clearing temperatures. Measurements of refractive indices of the two compounds were done by using thin prism method with He-Ne laser beam of wavelength 630 nm. Birefringence of the two LC compounds was calculated from the measured refractive indices. Both the compounds are found to display fairly high values of birefringence. Validation of a modified four-parameter model, based on Vuks equation describing the temperature dependence of refractive indices of the two liquid crystals, is also presented in this paper. The model is validated by fitting the experimentally measured values of refractive indices, birefringence and average refractive indices of the two nematic LCs with the theoretical values. In this paper, the calculation of order parameters of the LCs is presented by using two methods: direct extrapolation method based solely on the birefringence data and by using modified Vuks method based on Haller’s extrapolation. As observed from the obtained results, this procedure of calculating order parameter gives very reasonable results.     

K-Na离子交换单模平面波导的制备及其表征

通过K-Na离子交换技术制备了多模玻璃平面波导.采用棱镜耦合技术测量了波导的有效折射率,用IWKB方法拟合得到K-Na离子交换波导的折射率分布符合高斯分布,由色散曲线得到单模波导的制备条件(即扩散深度范围),从而得出单模波导的离子交换时间范围,制备出单模波导,并通过求解WKB色散方程得出单模波导的表面折射率.用普通数码相机,通过对离子交换平面玻璃光波导传输线进行数字成像,根据传输线上的光强分布拟合出光强传输衰减曲线,计算出单模波导的传输损耗大约为0.4 dB/cm.     

Guided-mode-leaky-mode-guided-mode fiber structure and its application to high refractive index sensing

We propose a fiber structure based on a single-mode-multimode-single-mode one. A theoretical analysis model based on leaky mode expansion along with a new concept of leaky mode interference is presented to facilitate and enlighten the analysis for the leaky structure. Then we focus on transmission characteristics of the structure in response to surrounding refractive indices (RI) that are higher than that of the silica fiber. In our simulation, output intensity of the structure increases monotonically for RI from 1.46 to 1.55, and changes over 2.0 dB for a change of 0.01 in RI range from 1.46 to 1.48, which is well verified by the following experiments.