Oxygen sensing using single frequencyGaAs-AlGaAs DFB laser diodes and VCSELs

Abstract
Oxygen detection using a GaAs-AlGaAs distributed feedback laser diode emitting at a wavelength of 761 nm is demonstrated for the first time. Using wavelength modulation spectroscopy with harmonic detection the authors have achieved a detection limit of 20 ppm.m with a lock-in amplifier time constant of 33.3 ms. The first results comparing the relative merits of VCSELs and DFB laser diodes for sensing applications are also shown.