Pressure Broadening Effects on the Output of a Gas Laser

Abstract

A model for a laser oscillator in which the atoms of the active medium do not collide during their radiative lifetimes has been used by Lamb. His theory predicts that as the cavity frequency is tuned through atomic resonance, there can be a dip in the intensity of the laser radiation. In the present work this model is generalized by allowing the atoms to collide while they radiate. The general formulation of the collision problem is presented for thermally moving neutral atoms interacting with a standing-wave cavity mode, and it is then applied to the calculation of the intensity profile for some simple collision models. It is found that as the pressure increases, not only is the "dip" broadened and made less deep, but it is also shifted and becomes asymmetric. Some observations by Cordover on pressure effects are found to be in satisfactory accord with this theory.