Stabilization of actively Q-switched lasers

The invention discloses an actively Q-switched laser with an intracavity nonlinear coupler in which a stable optical frequency converted output is generated. A Gain Fluctuation Insensitivity Condition is defined and described for several examples. The nonlinear coupler with a coupling level which satisfies this Condition permits stable laser operation with minimal interaction between pulses, evenwhen the pulses are clipped by the Q-switch. Thus, the output pulse duration and repetition frequency of the disclosed laser can be varied over a large range substantially independent of laser gain level and dynamics. Second and third harmonic optical frequency conversion is demonstrated, although the disclosed laser is applicable to other optical frequency conversion regimes as well.