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Modal analysis of a deep-etched low-contrast two-port beam splitter grating under Littrow mounting is presented. The guideline for the design of a subwavelength transmission fused-silica phase grating as high-efficiency grating, polarizing beam splitter (PBS), and two-port beam splitter, is summarized. As an example, a polarization-independent two-port beam splitter grating is designed at wavelength of 1064 nm. We firstly analyzed the physical essence of the grating by the simplified modal method. The guideline for the grating design and the approximate grating parameters are obtained. Then using the rigorous coupled-wave analysis (RCWA) with parameters varying around the approximate ones, optimum grating parameters can be determined. With the design guideline, the time for the rigorous calculation of the grating profile parameters can be reduced significantly. 相似文献
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The polarization selectivity is described based on the two-layer grating sandwiched between two fused-silica substrates. The polarization-selective grating can diffract TE polarization with high efficiency and split TM polarization with good uniformity. With the novel structure, the grating can have high efficiency of sandwiched grating and wideband property of two-layer grating. The modal method is applied to analyze the grating, which corresponds well with the results of rigorous coupled-wave analysis. The physical analysis can give the good guideline to optimize the polarization-selective sandwiched two-layer grating effectively. Such a polarization-selective grating can also have merits of high efficiency for TE polarization and wide angular bandwidth for TM polarization based on the two-layer grating sandwiched between two fused-silica substrate. It is easy to clean and protect the grating surface compared with the surface-relief grating. 相似文献
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Quantitative coherence analysis of dual phase grating x-ray interferometry with source grating 下载免费PDF全文
Dual phase grating x-ray interferometry is compatible with common imaging detectors,and abandons the use of an absorption analyzer grating to reduce the radiation dose.When using x-ray tubes,an absorbing source grating must be introduced into the dual phase grating interferometer.In order to attain a high fringe visibility,in this work we conduct a quantitative coherence analysis of dual phase grating interferometry to find how the source grating affects the fringe visibility.Theoretical analysis shows that with the generalized Lau condition satisfied,the fringe visibility is influenced by the duty cycle of the source grating and the transmission through the grating bar.And the influence of the source grating profile on the fringe visibility is independent of the phase grating type.Numerical results illustrate that the maximum achievable fringe visibility decreases significantly with increasing transmission in the grating bar.Under a given transmission,one can always find an optimal duty cycle to maximize the fringe visibility.These results can be used as general guidelines for designing and optimizing dual phase grating x-ray interferometers for potential applications. 相似文献
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光栅平动式光调制器结构参量的优化分析 总被引:4,自引:0,他引:4
提出的光栅平动式光调制器是一种基于微机电系统(MEMS)工艺的光调制器,利用其表面具有的变形部分(可动光栅)提供衍射光栅,通过控制可动光栅的位移实现光调制器的两种工作状态,即亮态和暗态。根据衍射理论和傅里叶光学对光栅平动式光调制器工作状态的光学特性进行了详细的理论分析和仿真。重点讨论了可动光栅占空比、长度L1、垂直光栅周期方向上边框长度、光栅栅条宽度、整个器件的光栅周期数等对光调制器工作性能的影响。结果表明,可动光栅与反射镜的距离为入射波长的一半时,调制器工作在暗态;而当可动光栅向反射镜方向下移入射波长的1/4时,光调制器工作在亮态;要达到最佳的衬比度,需满足可动光栅的栅条宽度为光栅周期的一半,L1应该为光栅周期的整数倍;在不满足L1为光栅周期d的整数倍时,可动光栅在垂直于光栅周期方向上的边框越小越好;光栅栅条越宽、光栅周期数越多,衬比度越高。 相似文献
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新近提出的光学色散元件"之"字形光栅具有优越的衍射特征,在光谱测量和分析中具有重要的应用价值.本文基于卷积定理,采用一种新的数值计算方法对应用于X射线波段的"之"字形光栅的衍射模式进行了模拟计算,并将其衍射模式与传统光栅以及正弦光栅的衍射模式进行了比对研究,结果表明:"之"字形光栅可以将高级衍射抑制到低于一级衍射四个量级的水平,具有比传统光栅优越得多的衍射模式,与理论预期结果一致.在此基础上,又分析了实际应用过程中吸收体对X射线的吸收情况给"之"字形光栅衍射模式带来的影响,最终证实了"之"字形光栅具有较强
关键词:
之字形光栅
卷积定理
衍射模式
光谱测量 相似文献
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Dot-matrix holograms created by two-beam writers contain many grating dots. Because the phase difference between two laser beams for interference cannot be controlled accurately, the fringe positions of grating dots are randomly determined. Therefore, fringe positions are a good kind of tool to identify dot-matrix holograms. In this paper, a number difference between two special fringes of a target grating dot is used to identify a dot-matrix hologram. The two special fringes are determined by three grating dots with parallel fringes. The first special fringe is corresponding to a fringe pair with the best matching for the fringes of the target grating dot and the fringes of the second grating dot. The second special fringe is corresponding to a fringe pair with the best matching for the fringes of the target grating dot and the fringes of the third grating dot. An experiment has proved the proposed method practical and feasible. Because reproducing a grating dot with a specified fringe number difference is difficult, the proposed method is excellent for anti-counterfeiting. 相似文献
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分析了将多块较小的光栅使用机械拼接的方式制成超大面积光栅,能解决大面积光栅目前无法整块生产的情况,在实际拼接中光栅会出现很微量的应力变形。根据拼接光栅通常的形变特点,采用标量衍射理论建立了光栅形变的理论模型,并就两块光栅拼接的情况进行了计算和分析,发现形变同拼接误差一样,会对光栅的远场光强产生负面影响,微小的变形量都对远场光强造成破坏,因此对衍射光场的影响不可忽略;获得了光栅机械形变的容限;最后给出了预防形变的措施:可着重减小y方向上约束,并使用多层介质膜光栅降低光栅对能量的吸收。 相似文献
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变栅距光栅线位移传感器是一种新型波长编码位移传感器,为进一步提高传感器波长解调的精度和减小光源的体积,提出适用于全工作波段的恒定闪耀角变栅距光栅结构。首先采用经典光学的方法推导出变栅距闪耀光栅衍射强度分布公式,从理论上证明该光栅结构可实现在全工作波段提高变栅距光栅线位移传感器衍射光强。此外,制作出变栅距闪耀光栅样件证实了工艺可行性。在相同的条件下,对一组参数相同的闪耀光栅和矩形槽形光栅进行了衍射光强比对实验,得到变栅距闪耀光栅的衍射光强约为矩形变栅距光栅的衍射光强的1.7倍,并与按此衍射光强分布公式计算的结果一致。 相似文献
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The generation of amplitude and phase gratings in an absorbing medium is discussed, including the effects of light polarization, population kinetics and orientational relaxation. A theory is given which describes light diffraction by a combination of an amplitude and a phase grating. It is shown that the coherent coupling effect in transient absorption measurements is solely due to the amplitude grating. Weak absorption and a low triplet yield favour diffraction of the probing beam by the phase grating in triple-beam experiments. Phase grating experiments can be performed with highly soluble absorber dyes, the absorption maximum of which is far away from the laser wavelength. Due to photoselection, diffraction by an amplitude grating depends on the polarization of the probing beam while phase grating diffraction is insensitive to this. Perpendicular polarization of the two exciting pulses prevents the buildup of a phase grating and results in light diffracted by the amplitude grating that is proportional to the transient dichroism signal as known from the common absorption relaxation. 相似文献
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长周期光纤光栅气敏薄膜传感器结构优化 总被引:11,自引:3,他引:8
基于三包层长周期光纤光栅模型,研究了包层表面涂覆一层溶胶凝胶气敏薄膜的长周期光纤光栅化学传感器的灵敏度Sn与薄膜光学参量(折射率n3和厚度h3)和光纤光栅结构参量(光栅周期、折变量和光栅长度)之间的关系。采用最优化数值方法,找到了获得高灵敏度所需的最佳膜层光学参量和光栅结构参量。理论计算表明,该类型传感器对膜层折射率的测量分辨率高达10-8。实验上制作了对乙醇气体敏感的传感器,并证实了传感器结构优化的必要性。 相似文献
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对探测光丝的不同位置与等离子光栅相互作用和探测光丝作用到等离子光栅不同位置引起三次谐波的增强进行了实验研究.研究发现,探测光丝的三次谐波信号强度对于探测光丝不同位置与等离子光栅相互作用和等离子光栅内部钳制的激光强度具有极强的依赖关系.与等离子光栅相互作用,三次谐波信号与等离子光栅基波信号的相位匹配与否是解释探测光丝三次谐波信号强度变化的关键.控制探测光丝以小角度与等离子光栅相互作用是实现探测光丝三次谐波信号有效放大的最佳途径. 相似文献
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Not only the grating material refractive index itself but also the Bragg grating physical shape formation affects the coupling strength greatly. The Bragg grating shape includes three factors, namely grating depth, duty ratio and grating angle. During the lithography and wet etching process, there always will be some fluctuation between the target and real grating shape formation after fabrication process. This grating shape fluctuation will affect the DFB coupling coefficient \(\kappa\), and then consequently threshold current and corresponding wavelength. This paper studied the grating shape formation fluctuation influence to improve the DFB fabrication yield. A truncated normal random distribution fluctuation is considered in this paper. The simulation results conclude that it is better to choose relative thicker grating depth with lower refractive index to obtain a better fabrication tolerance, while not quite necessary to spend too much effort on improving lithography and wet etching process to get a precisely grating duty ratio and grating angle. 相似文献
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Yuanshen Huang Dongyue Zhu Baicheng Li Dawei Zhang Zhengji Ni Songlin Zhuang 《Optik》2012,123(19):1797-1800
Based on the aberration theory of concave grating [1], [2], [3], a method to design aberration-corrected flat-field holographic concave gratings by parameter optimization is introduced. And the influence of different parameters such as the incident angle, effective grating grooves and grating radii on the aberrations at diffracted order ?1 is discussed. The results indicate that for a concave grating working in a given spectral range, we can correct aberrations by optimizing the incident angle. In addition, flat-field holographic concave gratings with higher resolution and lower aberration can also be designed by choosing the effective grating grooves and larger grating radius properly. 相似文献