Abstract

The application of laser absorption spectroscopy for remote sensing of environmental pollutants in the mid-infrared spectral range (MIR) is of fundamental interest, because most of the relevant molecules have strong vibrational transitions in this spectral region that can be used as “fingerprint” for a sensitive detection in complex environments, as air, water or soil. However, there is still a lack in simple, compact, portable and rugged MIR laser sources. In this context, diode-lasers and difference frequency generation recently have drawn considerable interest [1-3]. New and efficient nonlinear crystals, as e.g. AgGaS₂ or GaAsSe, and recent progress in the fabrication of fiber optics for the MIR make it possible to set up compact MIR laser spectrometers with the option of evanescent field spectroscopy. The latter one is of essential advantage when a detection of pollutants in optical thick media, e.g. soil, is required.

© 1998 Optical Society of America