Accurate gas diagnostics for sealed-off CO2 lasers using near-infrared DFB semiconductor lasers

The selective spectroscopic detection of CO2 and H2O in the gas mixture of a 400-W sealed-off CO2 slab laser is reported. The detection is based on the acquisition of absorption Voigt profiles of two vibrational overtone transitions of CO2 and H2O, obtained using two InGaAsP distributed feedback (DFB) semiconductor lasers, This spectroscopic method enables a direct absolute measurement of the temporal evolution for the concentrations inside the laser active volume. Monitoring takes place during laser operation without gas extraction. The experiments carried out on CO2 and H2O abundances confirm the paramount importance of wall desorbance phenomena in all-metal radio frequency (RF) excited lasers.