Ultra-Compact Fourier Transform Near-Infrared MEMS Spectral Sensor for Smart Industry and IoT

Abstract

Miniaturized spectrometers are being developed in the recent few years leveraging the rapidly-progressing technology and triggering new markets in the field of on-site and mobile spectroscopic analysis. Although some devices were commercialized for the near-infrared spectroscopy (NIRS), their size and cost still don't meet the requirements for the ubiquitous deployment of the spectrometer as a spectral sensor needed for the smart industry and IoT applications. In this work we report an integrated microelectromechanical system (MEMS)-based Fourier Transform Infrared (FT-IR) spectral sensor. A monolithic scanning Michelson interferometer MEMS chip and an extended InGaAs photodetector chip are integrated with a micro-optical system in a tiny package with a footprint of 18 mm, presenting the smallest reported FT-IR solution to date. A compact light source head is designed and implemented targeting diffuse-reflection applications. The reported sensor's spectral resolution is about 66.6 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> across the spectral range of 1350-2550 nm. The signal-to-noise ratio (SNR) achieved is 8000:1 at 2400 nm in 2 seconds, with an order of magnitude improvement with respect to previously reported fiber-coupled solution. The presented solution provides a low cost, low power, wide wavelength range NIR spectral sensor that can be manufactured with high volumes leveraging economies of scale.