Oxygen measurements at high pressures using a low-cost, polarisation-stabilized widely tunable vertical-cavity surface-emitting laser

Vertical-cavity surface-emitting lasers (VCSELs) are used for oxygen monitoring via tunable diode laser spectroscopy at 760nm wavelength. For the desired application, novel polarization-stable laser diodes based on AlGaAs were developed. We present measurements of the pressure-broadening coefficients of the electric dipole forbidden oxygen A-Band b1Sigmag + -> X3Sigmag + transition at 760nm. For the first time the pressure-broadening coefficients were determined with a temperature tuned vertical-cavity surface-emitting laser. Because of special techniques of polarization stabilization with a combination of a dielectric surface grating and a surface relief the VCSELs have a mode hop-free tuning range of more than 7nm and a sidemode suppression of more than 30dB. This provides a low cost las er diode system with a wide tuning range, which enables the possibility of simultaneous measurement of temperature, pressure and oxygen concentration in air, high pressure measurements and also a higher accuracy of oxygen concentration measurements due to averaging over 18 absorption lines.