GaSb-based lasers for gas monitoring

The wavelength range between 2 and 5 μm is of main interest for molecular spectroscopy and environmental monitoring. The 2.2-2.3 μm spectral region is a window for water vapor and CO₂ absorption while absorption lines of some atmospheric pollutants are very strong. One of the most sensitive techniques for selective gas analysis is tunable diode laser absorption spectroscopy (TDLAS). To reduce the cost and dimensions of the equipment, single frequency diode lasers and detectors operating in continuous wave (CW) regime at room temperature (RT) or above are required in this spectral range. In this contribution we summarize the results obtained in the development of 6.1 angstrom semiconductors diode lasers and their applications for trace gas detection. The laser structures were grown by molecular beam epitaxy on GaSb substrates. To estimate the spectral quality of the laser, emission mode maps of the lasers have been performed using a Fabry-Perot interferometer or directly absorption lines of gases of interest. We present some results on TDLAS of methane, carbon monoxide, carbon dioxide, and HF in trace concentrations, obtained with the GaSb diode lasers used in the CW regime at temperatures up to 800°C.