This book contains most, but regrettably not all, the papers that were presented at The Advanced Research Workshop, held July 1-5, 1997, at Smolenice Castle, Slovak Republic. The problem of angular divergence is of great importance in quantum electronics: low divergence is required not only in most of practical laser applications, but also for achieving high efficiency of parametric laser frequency conversion, and harmonic generation. The large volume of available studies aimed at improving the pump systems and the spectroscopic properties of lasing media, brought about no more than 2-3 fold increases in laser efficiency, while concurrent studies of angular divergence and the implementation of the findings, resulted in several order of magnitude of increases in radiance. The spatial beam structure that is formed in the laser cavity together with the active element constitute the most critical laser elements. The engineering devices, such as excitation systems, lasing gas circulation systems, etc., are usually at the top of the agenda of scientific meetings and of gatherings of engineering experts. The divergence problem has never been discussed by a broad community of experts in this field.
