Calculation of the minimum repetition rate of a cavity- dumped four-level laser

Calculations using the rate equations for an ideal 4-level laser system show that there is a minimum frequency below which efficient repetitive cavity dumping of a laser will not be stable. Expressions for the field and inversion variables are derived. Experimental results have been obtained using a folded cavity Nd-YAG laser that is perturbed by an intracavity acoustooptic modulator. The observed field inside the cavity is shown to behave like a damped harmonic oscillator. The minimum repetitive frequency, , of Stable operation is shown to increase with increased pumping rate and system loss and decrease with increasing laser cavity length. As a result, the minimum stable frequency depends on the strength of perturbation of the modulator since this adds loss to the system. The range of stable operation for the Nd-YAG laser under investigation varies from 135 kHz to several megahertz.