Power Scaling of End-Pumped Solid-State Rod Lasers by Longitudinal Dopant Concentration Gradients

The power scalability of solid-state rod lasers in general is limited by the thermally induced mechanical stress approaching the fracture stress of the laser material. In conventional end-pumped lasers, the spatial heat-generation density profiles follow a nearly exponential law, resulting in a reduction of the maximum possible pump power when compared with a transversally pumped rod of the same length. In this paper, an approach for power scaling of end-pumped solid-state lasers by employing crystals with longitudinally varying dopant concentration profiles is presented. The optimum continuously varying dopant concentration profiles for a pump-light single and double pass are derived. Multisegmented crystals approximate these continuous doping profiles. An algorithm for optimizing the segment lengths and dopant concentrations in these crystals is described, the resulting optimum segment data are tabulated, and the relative power capability of these crystals is given.