WAVELENGTH MODULATION DETECTION OF WATER-VAPOR WITH A VERTICAL-CAVITYSURFACE-EMITTING LASER

A vertical cavity surface-emitting laser was studied for gas-sensing a pplications. Properties of the 962-nm laser that were measured include side-mode suppression, wavelength tuning with temperature and current , power versus injection current, and the amplitude noise spectrum. Wi th wavelength modulation spectroscopy, a rms noise level of 2 x 10(-4) absorbance units was achieved. The large current tuning range (25 cm( -1)) and smaller amplitude modulation (11%/cm(-1)) of the vertical cav ity laser compare favorably with Fabry-Perot and distributed feedback diode lasers for spectroscopic gas sensing, especially at atmospheric pressure. (C) 1997 Optical Society of America.