Problems in the theory of recombination lasers

摘要

Experimental data is now available to provide a basis for a review of current theoretical understanding of recombination lasers. It is evident that whilst our models provide a qualitative picture of how these systems work, they are incapable of correctly estimating the gains measured. Several key discrepancies are apparent.rnWe shall examine these problems to attempt to identify the deficiencies in current modelling. In particular the zero trapping approximation is widely used on an empirical basis to predict the behaviour of experiments, but has no theoretical foundation. We examine the reduction in optical depth necessary to account for experimental data, and show it is crucial if simple short wavelength designs will operate. The theory of line trapping is reviewed and possible explanations of this problem explored.