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.