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.