Fabrication of a dual-tier thin film micropolarization array

Abstract

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 ~1000 in the blue and green visible spectrum and ~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 1μm under cutting of a 10μm 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. Abstract: 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 micro polarization filters retain the original extinction ratios of the unpatterned thin film. The measured extinction ratios on the micro polarization filters are ~1000 in the blue and green visible spectrum and ~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 underetching. Theoretical explanation for the optimum etching rate has also been presented. In addition, anisotropic etching with 1μm under cutting of a 10µm thick film has been achieved. Experimental results for the patterned structures under polarized light are presented. The array of micro polarizers will be deposited on top of a custom made CMOS imaging sensor in order to compute the first three Stokes parameters in real time.

Polarization image sensors: Learning from biology to make the invisible visible

“…Another approach uses a micro polarizer made with a birefringent crystal that is deposited on top of the imager [28,29]. Also nano-wire filters have been explored as an alternative approach to focal plane polarizer design [30][31][32][33]. A nano-wire polarization filter consists of narrow aluminum wires deposited on a glass substrate.…”

Advances in integrated polarization image sensors

“…15 degrees of maximum incident angle). Figure 1-a presents the PVA pixel-pitch-matched filter to the CMOS pixel after microfabrication with size of 10 m 3 [10].…”

Image sensor with focal plane polarization sensitivity

“…The procedures outlined bellow is an extension of the one described in [8]. In this paper we describe for the first time the complete process of fabricating and integrating a polymer polarization array with CMOS image sensor.…”