Frequency modulation spectroscopy with tunable diode lasers

SRI International has designed and built several instruments that use tunable diode lasers and frequency modulation spectroscopy. These instruments have been used for flux measurements of trace gases, explosives detection, and environmental monitoring. A detection sensitivity of 2X10-6 with a stability of 0.1% over 10 hours has been demonstrated using a GaAlAs laser and an oxygen absorption line at 760.56 nm.