Investigation and characterization of highly efficient near-infrared scanning gratings used in near-infrared microspectrometers

We present investigations of a new miniaturized NIR spectrometer with a size of only 10×8×8 cm3, and a MOEMS-scanning-grating chip as a main element. It works currently in a spectral range of 1200 to 1900 nm with a resolution of less than 10 nm using only one single InGaAs diode as a detector. One entire spectral measurement is done within 6 msec, calculated by a digital signal processor, which is included in the spectrometer. The MOEMS-scanning-grating chip is resonantly driven by a pulsed voltage of up to 36 V, has a grating plate 3×3 mm2, and reaches deflection angles of ±8 deg at 25 V. Control and investigation of the deflection angle, the static deformation, the spectral efficiency, and the mechanical shock resistance are key parameters to reach the spectrometer specifications. Results of these measurements and their influence on the spectrometer are discussed. Special etch control structures to monitor the fabrication process of the grating structure in the nanometer range, which can be easily done by microscopic inspection, are also presented.