Single MEMS Chip Enabling Dual Spectral-Range Infrared Micro-Spectrometer with Optimal Detectors

Abstract

Portable spectrometers enable rapid and low-cost material analysis in a ubiquitous manner by measuring their molecular absorption spectrum. To measure a wide variety of materials, it is essential to have a broad spectral range of operation with acceptable sensitivity. Recently, the miniaturization of Fourier transform infrared spectrometers has been realized using the micro-electro-mechanical systems technology. In this work, two identical Michelson interferometers are monolithically integrated on a silicon chip, in a parallel architecture, and their mirrors are driven by a single comb-drive actuator. The interferometers are fed by a broadband white light and their outputs are coupled to different photodetectors optimally selected for different spectral ranges. This enables an extended wavelength range of operation covering the near-infrared from 1.4 to 2.6 µm and the mid-infrared from 2.6 to 4.6 µm, simultaneously. Experimental results are obtained by using multimode optical fibers for light coupling between the components. The signal-to-noise ratio is measured and compared to theoretical expectations, showing good agreement. The spectral range of operation of the realized spectrometer is 1.4–4.6 µm (7142–2173 cm-1) with a spectral resolution of 31.5 cm-1. Finally, the spectrometer is used to acquire the transmission spectrum of polystyrene thin film and TS5 reference material.