Micro IR Spectrometer Based on Blaze Grating

An infrared spectrometer which employs a blaze grating as well as an 8-element thermopile array is designed, fabricated and tested in this paper. The grating which has 80 grooves of 19.2deg blazing angle and 5 mum grating constant is precisely defined by an anisotropic etching in KOH solution from a carefully cut silicon wafer. After bonded to wafers consisting of 8 Au-polysilicon line-shaped thermopiles and optical slit fabricated in IC-compatible processing, the blaze grating can diffract the incident light from the slit in a high efficiency, which improves the spectral resolution of the spectrometer significantly. With an optical path of the wafer thickness, the diffracted light will be detected by the thermopiles. Using a tunable laser source from 1510 nm to 1610 nm, the spectral resolution is determined as 60 in the spectrometer with 3times3times1.5 mm³ volume, which is about 5 times higher than a reported result with an ordinary multi-slit grating.