Abstract

Rate equation analyses of laser oscillator dynamics generally include an integrodifferential equation that describes the time dependence of the intracavity photon number.^1,2 This rate equation usually gives reasonable predictions for continuous-wave characteristics of low gain lasers. However, these predictions are inconsistent with Poynting’s theorem and disagree significantly with plane-wave calculations for high-gain lasers. It is often assumed that only first-order saturation effects are important² and that the laser mode is well-collimated within the gain medium.¹ I present a model of multimode laser oscillator dynamics that is consistent with both continuous-wave high-gain plane-wave analyses and rate-equation descriptions of Q-switched lasers. As an example, I describe a detailed analytic model of a continuous- wave high-gain end-pumped four-level laser, including thermal loading effects. I compute the maximum errors incurred by neglecting higher-order saturation terms and Gaussian beam expansion, and I simultaneously optimize both the output coupling and the laser mode waist.

© 1992 Optical Society of America