DEVELOPMENT OF A MEMS LAMELLAR GRATING SPECTROMETER FOR FOURIER TRANSFORM SPECTROSCOPY

Abstract

This thesis reports the design, fabrication and characterization of a lamellar grating-based Fourier Transform micro-spectrometer. The proposed device has a compact structure with low machining cost and can be potentially applied to determine the presence and compositions of chemicals through their signature spectra. It is realized through micro-electro-mechanical systems (MEMS) technology and mode of actuation is electrostatic parallel plate actuators. After obtaining an initial working prototype of the micro-spectrometer which is capable of achieving a full-width at half-maximum (FWHM) resolution of 9.8nm@532nm, two different approaches are subsequently adopted to improve its performance. The first is to actuate the model at its resonant mode; the spectral resolving capability of the model is found to be improved by a factor of 2. The second approach is to construct a cascaded spectrometer, which consists of two individual spectrometers with different initial optical path differences. A proposed algorithm is used to mathematically combine the scanning ranges of the two spectrometers, thus forming a spectrometer with a virtual elongated scanning range. The algorithm is verified experimentally and demonstrated to enhance the FWHM resolution of the micro-spectrometer by 100%.