Wide Spectral Range MEMS FTIR Spectrometer

Abstract

Development of miniaturized spectrometers for molecular analysis has gained great interest in the late few years for the sake of performing material identification and quantification everywhere and by everyone. Although many miniaturized spec-trometers are reported either in the literature or in the market, most of them have a limited spectral response in the visible or near-infrared (NIR) ranges. At the same time, most of the materials have their fundamental absorption peaks in the mid-infrared (MIR) range which are much stronger than their overtones in the NIR range. Among different spectroscopic methods, Fourier transform infrared (FTIR) spectros-copy has proved to be the most promising technique having no limit on the spectral range of operation. This work is based on bulk micro-machined free-space MEMS FTIR spec-trometer. Michelson interferometer with one moving mirror, the core engine of a Fou-rier transform spectrometer, is micro-fabricated on a single silicon chip using deep reactive ion etching (DRIE) technology. Optical coupling to MEMS chip is based on free-space coupling instead of optical fibers. A study on silicon absorption in MIR range is performed showing the limitations on the MEMS spectrometer range that may not occur in discrete bulk spectrometers. Different spectroscopic measurements are done validating the wide spectral range of MEMS spectrometer and its application in gas sensing with the different available sources and detectors.