MEMS tunable Fabry-Perot Filters with thick, two sided optical coatings

Abstract

A MEMS based tunable Fabry-Perot filter array has been designed and fabricated to provide spectral information in the long-wave infrared (LWIR) band, while remaining transparent in the mid-wave infrared (MWIR) band. Due to the stringent requirements on the optical design, relatively thick optical reflector and anti-reflector coatings are needed. A two-sided, SOI device layer transfer process has been developed to fabricate the thick coating layers and maintain a balanced stress state on the thin moveable membrane of the filter. Fabricated parts have less than 11 nm of deflection across a 200 mum filter. Measured filters show a <120 nm bandwidth peak in the LWIR that is tunable from 11.8 mum to 7.9 mum.