Abstract

The spatio-temporal evolution of the intracavity optical fields in a pulsed copper vapour laser (CYL) is of major importance when selecting the most suitable optical resonator configuration to generate high beam quality output from those devices. Laser action at 51 0.6nrn and 578.2nm in a CYL is characterised by a large small-signal gain (go -10-20m"'), large Fresnel number/large active volume, and short pulse duration which precludes the establishment of cavity modes within the resonator [1]. Significant round-trip modulation of the output beam intensity is also commonly observed and can be attributed to the spatially non-uniform amplification of the photon flux arising from spontaneous emission and subsequent gain saturation ef fects. Although a number of general analyses of the influence of the external resonator configuration in determing beam quality have been carried out [2], more detailed studies of the evolution of the intracavity fields including gain saturation in the active medium remain scarce [3]. Experimental measurements of the gain coefficient and laser field intensities, which give results with temporal, radial and longitudinal resolution, are problematic due to the inaccessibility of the active medium, the short pulse duration, and gain saturation by the probe.

© 1996 Optical Society of America