Silicon bolometer and micro variable infrared filter for CO/sub 2/ measurement

Abstract

We have developed silicon bolometers fabricated on an SOI wafer by bulk micromachining and a micro variable infrared filter, and have investigated CO/sub 2/ measurement using these elements as an NDIR system. The bolometer has a measured D* (1100 K, 10 Hz, 1 Hz) of 1.1/spl times/10/sup 8/ cmHz/sup 1/2//W. Two bolometers were combined with a micro variable infrared filter tuned to two different wavelengths: the CO/sub 2/ absorption band and the reference band. The two-wavelength NDIR system for combining these elements with the conventional infrared source was able to measure the concentration of CO/sub 2/ with the measurement reproducibility 3 /spl sigma/ of /spl plusmn/3.6% of the measured value or less between the concentrations of 0 ppm and 5000 ppm.