Real-time polarimeter with a form-birefringent micro retarder array

Abstract

We present the real time polarimeter with a micro retarder array consisting of subwavelength gratings with different directions. A 2x2 form-birefringent micro retarder array was fabricated with an electron-beam lithography method and a reactive ion etching technique. Each retarder was a TiO2 grating with 300-nm period on a silica substrate, and the phase retardance was 0.31 (pi) for 633-nm wavelength light. Using the fabricated retarder array, the real time polarimeter was made. The micro retarder array and a linear polarizer film were stacked up on a 2x2 photo-detector array. Four Stokes parameters were computed at a real time rate from outputs of the detector array. We could measure temporal change in polarization states of light by simple experiments.