Attenuated total reflection (ATR) MEMS FTIR spectrometer

In this work, we present a MEMS-based ATR FTIR spectrometer operating in the wavelength range of 1.8 μm to 6.8 μm. The core engine of the spectrometer is a monolithically integrated scanning Michelson interferometer on a silicon chip. The ATR crystal is illuminated with an IR source and the output light of the crystal is free-space coupled to the MEMS interferometer using micro-optics reflective mirrors and the modulated light from the interferometer is then coupled to an MCT photodetector. The recorded SNR of the spectrometer is about 1000:1 in 10 seconds measurement time with a spectral resolution of 66 cm-1. The spectra of different liquid samples were obtained and the effect of the ATR crystal refractive index on the absorption depth was investigated, showing good agreement with the theoretical model. The proposed miniaturized ATR MEMS spectrometer opens the door for various applications in oil analysis, food safety and health care among others.