Single-mode single-frequency laser with a self-filtering unstable cavity

A pulsed Nd:YAG laser with an unstable self-filtering confocal cavity and electronic narrowing of the spectrum is described. It generates single-mode single-frequency radiation with a smooth (near-Gaussian) transverse distribution of the intensity. The duration of a pulse at half-amplitude is 8 ns, the divergence is 0.7 mrad, and the energy is 20 mJ.