Measurement of the pressure broadening coefficients of the oxygen A-band using a low cost, polarization 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 760 nm 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 b(exp 1) Sigma+(exp 9) --> X(exp 3) Sigma+(exp 9) transition at 760 nm. The time the pressure-broadening coefficients were determined with a temperature tuned VCSEL. Generally temperature tuning has the disadvantage of frequent mode-hops, but the advantage of a wider tuning range in comparison to current tuning. 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 7 nm and a sidemode suppression of more than 30 dB. This provides a low cost laser 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.