Fabrication of a dual-tier thin film micropolarization array

A thin film polarization filter has been patterned and etched using reactive ion etching (RIE) in order to create 8 by 8 microns square periodic structures. The micropolarization filters retain the original extinction ratios of the unpatterned thin film. The measured extinction ratios on the micropolarization filters are approximately 1000 in the blue and green visible spectrum and approximately 100 in the red spectrum. Various gas combinations for RIE have been explored in order to determine the right concentration mix of CF(4) and O(2) that gives optimum etching rate, in terms of speed and under-etching. Theoretical explanation for the optimum etching rate has also been presented. In addition, anisotropic etching with 1 microm under cutting of a 10 microm thick film has been achieved. Experimental results for the patterned structures under polarized light are presented. The array of micropolarizers will be deposited on top of a custom made CMOS imaging sensor in order to compute the first three Stokes parameters in real time.