A Compact Near-Infrared Spectrometer based on an FR4 Electromagnetic Scanning Grating

Abstract

A novel small-scale near-infrared spectrometer based on an FR4-based scanning grating is presented. The design concept consists of a single FR4 printed circuit board ($110\ \text{mm} \times 76.5\ \text{mm}$) that integrates the entrance slit, exit slit, photodetector, scanning grating and all interfacing circuitry for scanner drive and sensor readout. The scanning grating consists of an aluminium-coated glass grating assembled on an FR4 square plate and is operated at resonance via electromagnetic actuation. The spectrometer design concept significantly facilitates alignment during product assembly and results in fewer parts. The spectrometer achieves a spectral range of 1210 nm to 2170 nm and an estimated spectral resolution of 10 nm using a single photodetector. The proposed optical configuration and the use of a single photodetector contribute towards a low-cost solution relative to the state-of-the-art. Moreover, superior scanning efficiency (0.13 degrees/mA) together with low power consumption (30 mW) and low operating frequency (190 Hz) are demonstrated with the FR4-based micro-scanner with an integrated diffraction grating.