PHOTOACOUSTIC GAS-DETECTION BASED ON EXTERNAL-CAVITY DIODE-LASER LIGHT-SOURCES

An external cavity diode laser is constructed and shown to have stable , narrow-linewidth operation around 840 nm. Based on this laser and a photoacoustic detector, a gas monitoring system capable of measuring a bsorption coefficients as low as 10(-8) cm(-1) is developed. The conti nuous (mode-hop-free) tuning range of the laser is found to exceed 100 GHz, which makes possible the spectrally resolved detection of water vapor absorption lines. The photoacoustic cell with the external cavit y diode laser as a light source offers great potential for the develop ment of a portable, automated gas detection system. (C) 1997 Society o f Photo-Optical Instrumentation Engineers.