The coupling of optical energy from a lamp into a laser rod using a spherical mirror enclosure has been analyzed using geometrical optics. The calculations indicate that about 75% coupling can be obtained for typical sized laser rods and spheres. Experimental results for a 3 mm × 30 mm Nd: Cr: YAG rod are given. Using external resonators, a slope efficiency of 1.15% and an output power of 3.4 W were observed for an input power of 870 W.
C. H. Church and I. Liberman, "The Spherical Reflector for Use in the Optical Pumping of Lasers," Appl. Opt. 6, 1966-1968 (1967)