MEMS-based microspectrometers for infrared sensing

Micro-electro-mechanical systems (MEMS)-based tunable optical filters, integrated with an infrared detector, select narrow wavelength bands in either the short-wavelength infrared (SWIR), or the mid-wavelength infrared (MWIR) region of the electromagnetic spectrum. The SWIR microspectrometer is based on monolithic integration of a parallel plate MEMS optical filter with a HgCdTe-based infrared detector. The fabrication process for the MEMS Fabry-Perot filter and the integral HgCdTe detector is completed while maintaining the processing temperature less than 125degC, as the performance of HgCdTe based detectors degrades at higher temperatrues. The preliminary MWIR microspectrometer result was based on a hybrid approach, fabricating the filter separately from the HgCdTe detector, however the process temperature control were maintained during fabrication of the MWIR filter, ensuring migration of this technology into an integrated solution. A tuning range of 900 nm with linewidths of 210 nm have been achieved for the MWIR, while maintaining a relatively low tuning voltage of 17 V.