Diode pumping of solid-state lasers with nonimaging optics: a theoretical study

Abstract

We have calculated the gain distribution within a circular absorbing medium that is pumped by a large-area planar-diode array by means of a nonimaging cavity design. The nonimaging cavity directs the light to the absorber, so there is negligible loss of pump light; a uniform gain distribution is achievable over the absorber cross-section. The gain uniformity is much better than current side- pumped geometries, and this leads to a higher-quality mode in the output beam. The nonimaging pump cavity requires a single reflecting surface. Therefore, problems due to alignment of the system should be reduced, and, in addition, the design is easily scalable. This design is compared to an elliptical (imaging) pump cavity design and to current diode pumping designs. We attempt to define concentration ratio,1 or effective étendue, for a nonplanar absorber. The concentration ratio is used as a figure of merit in comparisons between various nonimaging and imaging pump cavity designs.