Selective Gas Detection using Laser Based Photoacoustics

摘要

The new sensors developed by PAS-Tech are using laser based photoacoustics (PAS) for the detection of gaseous components and the analysis of gas mixtures. This method is based on the absorption of electro-magnetic radiation, the transfer of the absorbed energy into a sound wave and its detection with a microphone. Most sensors employ continuous-wave single-frequency diode lasers, such as Distributed Feedback (DFB) lasers. These exclude cross-sensitivity between different gas components and enable a very selective detection. DFB lasers can conveniently be operated at room-temperature. Their available emission wavelengths (0.8 μm - 3.0 μm) cover the important spectral range where many molecules have their strong fundamental vibrational absorption bands. For gases that require higher emission wavelengths (4 μm - 15 μm) Quantum Cascade Lasers (QCL) are employed Due to their extraordinary sensitivity and selectivity these powerful new sensors are suitable for numerous applications in the field of industrial process control as well as medical diagnostics In our contribution we will present details of the new technique as well as selected applications of laser based photoacoustics with particular emphasis of the range beyond wavelengths of 5 using QCL.