排序方式: 共有46条查询结果,搜索用时 500 毫秒
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A simple modal analysis (MA) method to explain the diffraction process of 0th order nulled phase mask is presented. In MA, multiple reflections of the grating modes at grating interfaces are considered by introducing equivalent Fresnel coefficients. Analytical expressions of the diffraction efficiencies and modal guidelines for the 0th order nulled phase grating design are also presented. The phase mask structure, which comprises a high-index contrast HfO 2 grating and a fused-silica substrate, is optimized using rigorous coupled-wave analysis around the 800-nm wavelength, after which the modal guideline for cancellation of the 0th order in a phase mask is verified. The proposed MA method illustrates the inherent physical mechanism of multiple reflections of the grating modes in the diffraction process, which can help to analyze and design both low-contrast and high-contrast gratings. 相似文献
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A simplified modal method to explain the resonance phenomenon in guided mode resonance(GMR) gratings with asymmetric coatings is presented.The resonance observed is due to the interaction of two propagation modes inside the grating.The reflectivity spectra and electric field distributions calculated from the simplified modal method are compared using rigorous coupled-wave analysis(RCWA).The influences of high-order evanescent modes on the resonance peak are analyzed.A matrix Fabry-Perot(FP) resonance condition is developed to evaluate the resonance wavelength.An explanation for the resonance phenomenon observed based on the FP resonance phase condition is also proposed and demonstrated.The simplified method provides clear physical insights into GMR gratings that are useful for the analysis of a variety of other resonance gratings. 相似文献
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We report a laser writing system for fabrication of diffractive optical elements with He-Cd laser. The wavelength of the light source is 441.6 nm. The output beam is collimated into parallel light with uniform intensity distribution after passing through the spatial filter with a pinhole of 25μm and the collimating device. A microscopy objective lens with numerical aperture (NA) of 0.65 is used to focus the beam into a small diffraction spot. Any pattern can be written with this system. Experimental results are presented. The written gratings and the phase patterns were verified with a conventional optical microscopy and the Taylor Hobson equipment. 相似文献
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用矢量衍射方法分析了线偏振光入射到带有三环位相型光瞳滤波器的高数值孔径物镜时,焦点的轴向和横向光强分布.数值模拟结果表明,高数值孔径物镜聚焦时需同时考虑光强的轴向和横向分布.通过加入三环位相光瞳滤波器,在实现横向超分辨的同时实现了光学系统轴向焦深扩展和轴向光强分布平坦化,并且位相调制深度变化时,会出现轴向焦移现象.对三环位相光瞳滤波器结构进行了优化,得出了优化结果.
关键词:
光学超分辨
扩展焦深
位相型光瞳滤波器
矢量衍射方法 相似文献
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A deep binary silicon grating as high-extinction-ratio reflective polarizing beam splitter (PBS) at the wavelength of 1550 nm is presented. The design is based on the phenomenon of total internal reflection (TIR) by using the rigorous coupled wave analysis (RCWA). The extinction ratio of the rectangular PBS grating can reach 2.5~105 with the optimum grating period of 397 nm and groove depth of 1.092 μm. The efficiencies of TM-polarized wave in the 0th order and TE-polarized wave in the -1st order can both reach unity at the Littrow angle. Holographic recording technology and inductively coupled plasma (ICP) etching could be used to fabricate the silicon PBS grating. 相似文献
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Analyses and computations of asymmetric Z-scan for large phase shift from diffraction theory 总被引:1,自引:0,他引:1
Based on Presnel-Kirchhoff diffraction theory, we set up a diffraction model of nonlinear optical media to Gaussian beam, which can interpret the Z-scan phenomenon from a new way. This theory is not only well consistent with the conventional Z-scan theory in the case of small nonlinear phase shift, but also can fit for the lager nonlinear phase shift. Numeric computations indicate the shape of the .Z-scan curve is greatly affected by the value of the nonlinear phase shift. The symmetric dispersion-like Z-scan curve is only valid for small nonlinear phase shift (|Δφ0| < π), but with increasing the nonlinear phase shift, the valley of the transmittance is severely suppressed and the peak is greatly enhanced. Further calculations show some new interesting results. 相似文献
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