Diode-Laser-Based Detection of BTXE-Aromatics in Oil Polluted Soil Samples

Abstract

The generation of tunable laser radiation in the spectral range between 4 and 10 µm is of general interest for the spectroscopy since most of the fundamental vibrational modes of molecules are within this spectral region [1]. There exist several conventional tunable cw-laser systems, like lead salt-diodes, color center-, optical parametric-, and CO or CO2 side band lasers. However, they need cryogenic cooling, do not cover all spectral regions that are of general interest for the spectroscopy and in most cases they are very complicated and complex laser sources. This limits the possibilities for practical applications of mid-infrared absorption spectroscopy, e.g. in the trace analysis of environmental pollutants. Therefore there is still a lack in simple, compact, portable, and rugged mid-infrared laser sources. In this context diode-lasers and difference frequency generation (DFG) in new nonlinear media such as AgGaS2 have drawn considerable interest in the construction of compact cw laser spectrometers [2,3].