Effects of small-scale phase perturbations on laser oscillator beam quality

A simplified analysis is presented for predicting the effects of small-scale intracavity phase perturbations or scattering centers on the power output and beam quality of high-power laser oscillators. The small-scale perturbations are viewed as scattering energy from the unperturbed lowest order transverse mode of the cavity into numerous higher order transverse modes. These modes are, unfortunately, then regeneratively amplified within the laser cavity. This produces only a small change in the effective output coupling and the total power output from the perturbed laser cavity, but causes a serious deterioration in the far-field brightness and on-axis intensity of the output beam.