Influence of collisions on radiative saturation and Lamb dip formation in CO2molecular lasers

Saturated gain profile measurements in CO2at pressures where a Lamb dip appears in the laser intensity reveal that individual rotation-vibration transitions saturate with a strong Doppler component in addition to the Lorentzian holes expected for a Doppler broadened line. This mixed inhomogeneous-homogeneous behavior represents cross-relaxation effects induced by collisions that change the molecule´s velocity. A rate equation formulation of collision effects elucidates the role of elastic and rotational thermalizing collisions on saturation and Lamb dip formation in molecular lasers.