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1.
Electromagnetic TM modes of metallic lamellar reflection or transmission gratings are analyzed by means of the parametric fourier modal method. We show that the resonant optical response of such devices is due to the excitation of guided waves inside the slits. Our rigorous methods allows us to define a resonance condition number and to calculate the field everywhere inside the grating layer. 相似文献
2.
提出了一种基于二维亚波长光栅的具有非偏振光入射下入射角不敏感特性的反射式颜色滤光片. 采用严格耦合波分析方法详细分析了光栅周期、光栅层厚度以及固定光栅占空比下光栅的结构尺寸对反射率峰值、反射带位置及带宽的影响. 结合入射角不敏感特性, 经过优化设计得到了光栅的最终结构参数, 获得了中心波长424 nm, 峰值反射率56%, 带宽45 nm的反射滤光片.模拟结果表明, 在非偏振光入射下, 此滤光片的反射光谱表现出显著的入射角不敏感特性. 当入射角高达60°时反射带的中心波长偏移6 nm 反射率下降6%带宽增加8 nm 其参数没有较大变化通过调整光栅的结构参数可在400–520 nm范围内调节滤光片的中心波长以获得不同颜色的入射角不敏感滤光片.
关键词:
反射式滤光片
二维亚波长光栅
入射角不敏感
严格耦合波分析 相似文献
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采用傅里叶模方法,分析了单点金刚石铣削后KDP晶体表面小尺度波纹的周期和幅值对单层增透膜折射率、厚度以及透射率的影响。研究表明:膜层最佳折射率在1.22左右,在此折射率条件下,保证透射率大于99%的单层增透膜的理想厚度范围应为180~220 nm,并且折射率和膜厚值的选取基本不受晶体表面小尺度波纹周期和幅值的影响。若只考虑SPDT法加工后KDP晶体表面小尺度波纹周期和幅值的实际范围,透射率基本不受波纹周期的影响,但却会随波纹幅值的增大而加速下降。理想镀膜条件下透射率最大值大于99%,并且通常在99.67%~99.94%之间。 相似文献
5.
A. V. Tishchenko 《Optical and Quantum Electronics》2005,37(1-3):309-330
Some remarkable effects are analyzed at the light of the ‘vertical mode’ representation of diffraction on a deep lamellar grating such as total diffraction in transmission and resonant total reflection. The general methodology of this phenomenological representation is given together with rigorous numerical examples. 相似文献
6.
The Fourier modal method for crossed gratings is reformulated by use of a group-theoretic approach when the grating structures have the equilateral triangular symmetry. In the new formulation, a grating problem is first decomposed into four symmetrical basis problems whose field distributions are the symmetry modes (two are nondegenerate and the other two are doubly degenerate) of the grating. Then the symmetry relations of fields in the symmetry modes are used to reduce the number of unknowns in numerical computation. After the symmetrical basis problems are solved, their solutions are superposed to get the solution of the original problem. It is shown that when the grating is at some incident mountings, the memory occupation can be saved by 2/3 and the computation time can be reduced to 1/12 to 1/13.5 of the original one for different incident cases. Numerical examples are given to illustrate the effectiveness of the new formulation and verify the improved computation efficiency. 相似文献
7.
利用傅里叶模式理论分析了TE波自准直角入射的使用条件下,多层介质膜光栅的光栅区和多层膜区电场分布的特点.分别讨论了HfO2和SiO2为顶层光栅材料时,光栅结构参数对光栅脊峰值电场的影响,结果表明,对于不同膜厚的顶层材料,存在一个最佳膜厚度,使光栅脊峰值电场最小,并且当膜厚增大时,设计大高宽比的光栅可以降低该电场峰值.最后,在大角度条件下使用多层膜光栅也可以降低光栅脊处的峰值电场.
关键词:
衍射光学
多层介质膜光栅
模式理论
损伤阈值 相似文献
8.
采用傅里叶模方法,分析了单点金刚石铣削后KDP晶体表面小尺度波纹的周期和幅值对单层增透膜折射率、厚度以及透射率的影响。研究表明:膜层最佳折射率在1.22左右,在此折射率条件下,保证透射率大于99%的单层增透膜的理想厚度范围应为180~220 nm,并且折射率和膜厚值的选取基本不受晶体表面小尺度波纹周期和幅值的影响。若只考虑SPDT法加工后KDP晶体表面小尺度波纹周期和幅值的实际范围,透射率基本不受波纹周期的影响,但却会随波纹幅值的增大而加速下降。理想镀膜条件下透射率最大值大于99%,并且通常在99.67%~99.94%之间。 相似文献
9.
Shijie Liu Zicai Shen Weijing Kong Jian Shen Zhenxia Deng Yuanan Zhao Zhengxiu Fan 《Optics Communications》2006,267(1):50-57
Multi-layer dielectric (MLD) gratings for pulse compressors in high-energy laser systems should provide high diffraction efficiency as well as high laser induced damage thresholds (LIDT). Nonuniform optical near-field distribution is one of the important factors to limit their damage resistant capabilities. Electric field distributions in the gratings and multi-layer film region are analyzed by using Fourier modal method. Optimization of peak electric field in the gratings ridge is performed with a merit function, including both diffraction efficiency and electric field enhancement when the top layer material is HfO2 and SiO2, respectively. A set of optimized gratings parameters is obtained for each structure, which reduce the peak electric field within the gratings ridge to being respective 1.39 and 1.84 times the value of incident light respectively. Finally, we also discuss the effects of gratings refractive index, gratings sidewall angle and incident angle on peak electric field in the gratings ridge. 相似文献
10.
The eigenvalue problem discussed in Noponen and Turunen [Eigenmode method for electromagnetic synthesis of diffractive elements with three-dimensional profiles, J. Opt. Soc. Am. A 11 (1994) 2494–2502] for crossed gratings is analyzed in a different way using the three components of the electric field instead of the components Ex,y, Hx,y. As a result, half as many eigenvectors are needed. 相似文献
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针对惯性约束聚变(ICF)终端光学系统对元件数量及厚度的限制,利用衍射光学元件(DOE)易于集成的优点,可将终端光学系统中实现不同功能的DOE元件集成于一体,以优化系统的结构和性能.为了对ICF终端光学系统集成光学元件在强激光条件下的正常运行提供分析的依据,采用傅里叶模式理论分别对色分离光栅(CSG)和色分离光栅-光束取样光栅(CSG-BSG)集成光学元件内部的近场调制特性进行了模拟计算.计算发现,将CSG与BSG集成以后其每一层的最大调制度比集成以前小10%—47%,但其激光诱导损伤风险和单个CSG一样
关键词:
色分离光栅-光束取样光栅集成光学元件
激光诱导损伤
惯性约束聚变
傅里叶模式法 相似文献
12.
The parametric formulation of the combined boundary conditions method (CBCM) with spatial adaptive resolution is extended to multilayered structures of strip gratings. Furthermore, it is shown that it is not necessary to solve the eigenvalue problem in all the layers of these structures; leading to drastic reduction of the computational load. 相似文献
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In this paper, a fractional partial differential equation (FPDE) describing sub-diffusion is considered. An implicit difference approximation scheme (IDAS) for solving a FPDE is presented. We propose a Fourier method for analyzing the stability and convergence of the IDAS, derive the global accuracy of the IDAS, and discuss the solvability. Finally, numerical examples are given to compare with the exact solution for the order of convergence, and simulate the fractional dynamical systems. 相似文献
16.
To model chirped fiber Bragg gratings (FBGs) for dispersion compensation in optical fibers a novel method of single expression
(MSE) is used. The reformulation of Helmholtz’s equation in the MSE to the full set of first-order differential equations
leads to dealing with the electric field amplitude, its derivative, power flow density and phase distributions in any aperiodic
media. The phase derivative obtained numerically permits to compute the dispersion slope in the time delay of investigated
chirped gratings. Reflective and time delay spectra of linearly chirped gratings of different lengths and chirp coefficients
are computed. A self-similarity law for the gratings of the same strength but different lengths and chirp coefficients is
revealed. The apodization of gratings is applied to reduce sidelobes in gratings’ reflection spectra and eliminate oscillations
in the time delay characteristics. 相似文献
17.
To model chirped fiber Bragg gratings (FBGs) for dispersion compensation in optical fibers a novel method of single expression (MSE) is used. The reformulation of Helmholtz's equation in the MSE to the full set of first-order differential equations leads to dealing with the electric field amplitude, its derivative, power flow density and phase distributions in any aperiodic media. The phase derivative obtained numerically permits to compute the dispersion slope in the time delay of investigated chirped gratings. Reflective and time delay spectra of linearly chirped gratings of different lengths and chirp coefficients are computed. A self-similarity law for the gratings of the same strength but different lengths and chirp coefficients is revealed. The apodization of gratings is applied to reduce sidelobes in gratings' reflection spectra and eliminate oscillations in the time delay characteristics. 相似文献
18.
提出了一种基于分数阶傅里叶变换的模式测控一体化方法。利用分数阶傅里叶变换光路对光纤模式耦合态进行空间调制和相位调制,以实现模式的有效分解。与双重傅里叶变换(F2)法以及空间和频谱成像(S2)法相比,采用的分数阶傅里叶变换法,通过改变分数阶参数,控制模式的空间分布以及模式间的叠加状态,更易于分解出高阶模式。基于分数阶傅里叶变换的模式测量方法可在更广泛空间,研究模式的空间和相位叠加以及模式分解,也可退化为F2法和S2法。 相似文献
19.
利用傅里叶模方法分析厚层光刻胶内衍射光场 总被引:2,自引:2,他引:0
建立了描述厚层光刻胶内衍射光场形成过程的物理模型,并利用傅里叶模方法模拟计算和分析了其内部衍射光场分布。该方法考虑了其界面反射、透射及光刻胶复折射率在空间上的缓慢变化对衍射光场的影响,采用该方法模拟光刻胶内衍射光场具有数值计算结果准确、计算速度快的优点。对厚层光刻胶折射率在几种特殊分布情况下衍射光场分布的数值模拟表明,衍射光场与其复折射率的空间分布有关。由于厚层光刻胶折射率在空间上呈缓慢变化的特点,为降低其数值计算量和编程难度,可以将厚层光刻胶近似为折射率随曝光时间变化的光栅。 相似文献
20.
傅里叶变换红外光谱(FTIR)成像技术可同时获得组织样本的空间分布信息和红外光谱信息。本文利用FTIR成像技术对离体原位乳腺组织样本进行原位研究,通过特征谱带吸光度比值(面积比值)图像结合FTIR光谱分析研究健康和癌变乳腺组织的差异。发现乳腺癌组织的特征带吸光度比值A1087/A1455、A1238/A1455、A1550/A1455、A1650/A1455相对于健康组织明显增大,A1160/A1087、A1740/A1550则减小。研究结果论证了乳腺组织癌变过程中大分子含量的变化规律,体现了FTIR成像技术在乳腺癌诊断方面的准确性、直观性和可行性,其有潜力成为基础研究和临床诊断的一种准确有效的技术手段。 相似文献