共查询到19条相似文献,搜索用时 125 毫秒
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局域体全息光栅的衍射特性 总被引:7,自引:5,他引:2
基于三维耦合波理论,研究了两束有限宽度的任意偏振平面波干涉产生的局域体全息光栅的衍射问题。以单位均匀振幅的任意偏振平面波为例,给出了透射波和衍射波振幅的主分量和交叉分量的解析表达式,讨论了记录过程和再现过程中入射的参考光波的偏振角对透射波和衍射波振幅的影响。计算结果表明,记录过程中的偏振角越小,形成的光栅内的耦合越强,衍射效率越高,但光束质量越差;再现过程中不同的偏振角,由于入射波和衍射波的电矢量的不同方向的耦合强弱不同,透射波和衍射波振幅的主分量和交叉分量的振幅变化行为不同。 相似文献
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基于严格耦合波理论分析了一种非对称偏振分束光栅的设计。这种偏振分束光栅分别在1级和0级衍射级次上衍射TE和TM偏振波。介绍了利用遗传算法设计偏振分束光栅的方法,并给出了优化实例。仿真结果表明:在设计波长为1.55时,TE偏振波在1级的衍射效率大于93%,TM偏振波在0级的衍射效率大于99%,此时1级和0级的透射消光比分别达到了9914.1和46841.5。通过对设计结果的分析发现,该偏振分束光栅在设计波长附近100nm的波长范围内都具有较高的消光比(大于100),达到了较好的偏振分束效果。 相似文献
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高密度光栅具有与传统光栅不同的性质,其衍射特性往往是偏振相关的。本文针对1550nm波长TE/TM偏振入射光和0.5的光栅占空比,利用严格耦合波分析数值计算了不同光栅周期下0级及-1级的衍射效率。研究表明,相比周期为1550nm的光栅,当周期为1200nm时,偏振相关衍射效应明显增强,当光栅周期为890nm时,TE偏振光的衍射效率随着光栅深度呈正余弦变化,而TM偏振光的衍射效率始终集中在0级,具有偏振选择性。通过模式方法,利用模式中的有效折射率概念,研究了不同周期下被入射光所激发的两种光波模式通过光栅区域传播所累积的相位差;基于双光束干涉,模拟了0级和-1级的衍射效率。结果表明,利用严格耦合波分析的数值计算结果符合模式方法的理论预期,对于高密度相位光栅的偏振选择性给予了合理的物理机制解释。 相似文献
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Ce:KNSBN光折变晶体栅衍射特性研究 总被引:2,自引:1,他引:1
研究了Ce:KNSBN光折变晶体两波耦合作用写入体光栅的衍射效率与写入光偏振态和光强比的关系,分析了写入光偏振态造成光栅衍射效率差别的原因,并用修正耦合波理论对实验进行了拟合。实验结果为Ce:KNSBN晶体在全息记录和光学信息处理领域的应用提供了依据。 相似文献
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J. Qiu L.H. Liu P.-f. Hsu 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(12-13):1912-1920
Metallic triangular grating structures have a wide range of applications. This study focuses on the radiative properties of triangular grating structures of aluminum in the mid-infrared wavelength to determine if we can tailor the infrared radiative properties by designing special geometrical details into triangular grating surfaces. Fabrication of triangular gratings within the range of micron scale is very difficult. Therefore, the influences of slight geometry modification, generated by fabrication errors, on radiative properties of triangular gratings are mainly investigated. The electromagnetic wave scattering from such surfaces is predicted by solving Maxwell's equations using the finite-difference time-domain (FDTD) method. The results show that the spectral reflectance varies with the dimensions of triangular gratings, which is due to the excitation of surface wave by confirmation of the EM fields. It is found that the spectral reflectance can also be reduced by increasing the height of slight geometry modification. The effect of oblique incident wave state is also investigated. An optical vortex is found due to the coupling of surface waves, the oblique incident wave and the scattering waves. This study helps to gain a better understanding of the radiative properties of metallic triangular gratings with slight geometry modification and will have an impact on triangular grating processing. 相似文献
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The system of partial differential equations for moving optical solitons in fiber Bragg gratings are studied. The traveling wave reductions are used to look for solutions of the system of equations. The compatibility conditions for the overdetermined system of equations are analyzed and discussed. Periodic and solitary waves in optical fiber gratings are found and illustrated. 相似文献
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Hybrid technique of finite element method (FEM) and Gaussian mode expansion method is implemented for the analysis of transmission
property of dielectric phase gratings used in holographic power combining systems. It takes advantages of the versatility
of FEM and the simplicity of the mode expansion method. Apparently, this hybrid method is well suited for the analysis of
phase gratings with complex profiles, which provide more degrees of structural freedom than those of classical rectangular
groove gratings. The transmitted fields of an array of two and three fundamental Gaussian beams through the multi-stepped
and curved gratings are calculated by the hybrid method. Numerical results show that much less phase distortion can be fulfilled
for the reconstructed pseudo-plane wave by the modified phase gratings, especially the curved ones. This is advantageous for
improving the combining efficiency in spatial millimeter wave and sub-millimeter wave power combining systems. 相似文献
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R. S. Avakian K. R. Aghababian M. Ts. Aivazian Yu. N. Kazantsev 《International Journal of Infrared and Millimeter Waves》1995,16(2):411-418
Electromagnetic wave propagation is conside-red through a waveguide system consisting of arbitrary number of short-period gratings (i.e. whose period is much shorter than the wave-length). We assume that gratings are formed by ideal conductors having arbitrary cross-section. In order to "stitch" together the fields on gratings, equivalent boundary conditions are used.We have analyzed and studied experimentally the electrical characteristics of an adjustable frequency filter. The filter consists of three short-period gratings formed by conductors with circular cross-section.Experimental results are in good agreement with theory. 相似文献
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A novel method for measuring the three-dimensional spatial distribution of gratings in a volume holographic medium is described. In this method, the diffraction of a uniform probe light wave is measured as a function of the deviation (either in angle or wavelength) from the Bragg condition. The envelope function of the grating is obtained by solving the coupled wave equations inversely. Not only the amplitude but also the phase of the envelope function is obtained. This method allows for the depletion of the probe light wave in the hologram and is applicable to both dielectric (refractive index) and absorption gratings. The resolution and the maximum measurable depth in this method are discussed. 相似文献
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对特定介质中的光学稳态简并四波混频过程进行了数学描述,并对四波混频耦合波方程组作了数学推导,指出四波混频中有关参量之间的关系和特性。 相似文献
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The problem of diffraction by simultaneously existing surface-profile and impedance gratings in the presence of resonance with a surface electromagnetic wave is examined. The problem is solved in an impedance approximation (Leontovich boundary condition) using Rayleigh's hypothesis. The solution method is based on the distinguishing of resonance fields, for which a finite system of equations is constructed. A proposed regular procedure for exclusion of nonresonance fields makes it possible to obtain a solution with any accuracy for any polarization of the incident radiation and orientation of the gratings. Specific results are given in a principal approximation for the case of several resonances in the first-order spectra.Scientific-Industrial Organization Metrology. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, Nos. 3, 4, pp. 234–245, March–April, 1992. 相似文献
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We have investigated the photodiffractive effect induced by resonant excitations in semiconductor microstructures by means of the multiple wave coupling method. We have derived set of multiple wave coupling equations for photodiffractions in the case of coexistence of refraction and absorption gratings. Numerical results of the equations for a few typical cases have been analysed in detail, and their physical significance is also discussed. 相似文献