Abstract

Optical gas sensors using laser diodes have received attention because they satisfy air-monitoring requirements. Various sensor configurations have been proposed and developed that are basically applications of laser spectroscopy methods. Because of this, it is necessary to extend the length of the optical absorption path to enhance the sensitivity. To overcome this problem, our earlier work proposed an optical fiber gas sensor based on a thermal lens (TL) spectroscopy technique.^[1] One feature of our technique is that the optical absorption path is much shorter (usually 20-50 (μm) compared with other optical spectroscopy techniques. In our previous apparatus, it is necessary to use a wavelength-tunable laser diode as the light source for pumping the TL. However, this laser diode was not only extremely expensive but also troublesome because it required accurate wavelength adjustments. Additionally, the coverage of the tunable wavelength was extremely narrow in commercial laser diodes, limiting the ability to sense typical gases.

© 2007 IEEE