We report the design, fabrication, and test results of a tunable pyroelectric detector with an integrated micromachined Fabry-Perot (FP) filter for gas analysis in the mid-wave infrared (MWIR). The new approach is based on a bulk micromachined Fabry-Perot interferometer with an air cavity, which is electrostatically tuned. Various types of movable reflectors and spring configurations are fabricated to determine the optimum solution with respect to maximum tuning range, low gravity influence on center wavelength, and suitable filter bandwidth. Short and long cavity filters are designed for the spectral ranges of 3 to 4.3 ?m and 3.7 to 5.0 ?m, respectively. The tunable filter is arranged on top of a current mode pyroelectric detector with a flat spectral response. It is shown that the main challenge is to achieve a high finesse in spite of nonperfect parallelism, mirror curvature, and the additional phase shift caused by the Bragg reflectors
This paper reports design, fabrication and test results of a tunable pyroelectric detector with an integrated micromachined Fabry-Perot (FP) filter for gas analysis in the Mid-Wave Infrared (MWIR). The new approach is based on a bulk micromachined Fabry-Perot interferometer with an air cavity, which is electrostatically tuned. Various types of moveable reflectors and spring configurations have been fabricated to determine the optimum solution with respect to maximum tuning range, low gravity influence on center wavelength and suitable filter bandwidth. Short and long cavity filters were designed for the spectral ranges of 3...4.3 m and 3.7...5.0 m respectively. The tunable filter is arranged on top of a current mode pyroelectric detector with a flat spectral response. It could be shown that the main challenge is to achieve a high finesse in spite of non-perfect parallelism, mirror curvature and additional phase shift caused by the Bragg reflectors
A tunable dual-band MEMS Fabry-Pérot filter for simultaneous use of the spectral ranges from 8 µm to 10.5 µm and from 4 µm to 5 µm is reported. A peak transmittance of at least 75 % and a FWHM of less than 200 nm were measured. The maximum control voltage is 41 V. Two movable reflector carriers compensate the influence of gravitational force on the central wavelength. The device can withstand mechanical shocks according to Mil-Std-883G, method 2002.4, test condition B. The filter is integrated in a tiny, robust and fast microspectrometer module with the size of a TO-8 housing.
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