Research On The Radial Polarized Grating Mirror

Radial polarized light has many unique advantages compared to traditional linearlypolarized light, it can take advantages of the polarization characteristics in the captureand manipulation of particle, metal processing and improving of the microscope. Atpresent, people have several methods generated a radial polarized light, mainly seper-ated intra-cavity and the out-cavity.Presently, the method to calculate the multilayer gratings has matured, the T-matrixalgorithm and the S-matrix algorithms have been successfully applied to the grating’stheoretical calculation. These two algorithms have the common part of the basisassumptions. In the T-matrix, the feedback effect of the reflected light in the un-derlying film is ignored in the grating’s diffraction process, yet S-matrix one give afull consideration to this factor. Then we make a comparison between a commercialS-matrix program with a T-matrix program edited by myself in a top-etching model.The result showed that there’s no apparent difference in the top-etching grating exceptcomputing the duty, but the T-matrix program could be more stable and convenient.In this paper, two grating models were built which contained top-etching multilayerfilm grating and the bottom-etching multilayer grating. Based on the S-matrix andT-matrix algorithm program, we analyzed the factors’ influence to the TM/TEpolarized lights’ reflectivity such as the groove depth, period, layer number, dutycycle, and the angle of incidence. Finally found that the two grating models’ TM lightreflection curve only slightly affected by the groove depth and not sensitive to otherfactors; TE-ray reflectivity curves is obvious affected by the groove depth and period,while not sensitive to the number of layers and duty ratio. And by observing theresults, two grating’s curves have a visible gap in the TE reflectivity curve depressioncenter when chosen a suitable slot depth, and by adjusting the cycle, this depressioncenter will move to the desired band, to achieve a polarization selectivity in particularwavelength.Considering the calculations and analysis on the top-etching multilayer grating andthe bottom-etching multilayer grating, and the existed processing conditions, wedetermined to design a intra-cavity top-etching multilayer grating which has acomposite structure, by chosen a suitable grating groove depth, period, duty cycle andnumber of layers, the TM polarized light reflectivity and TE-polarized lightreflectivity will have a visible difference in the TE reflectivity curve depression center(TM light reflectivity>98%，TE reflectivity of <90%).This gap between these twopolarized light will inhibit the TE light and enhance the TM light. So we could get aradial polarized light’s output by intra-cavity grating at1064nm band.