Abstract: A multimode source, such as a high-power laser diode bar, to pump an Nd3+ doped region defined in a cavity of a monolithic crystal structure. The axial length L1 of the doped region is chosen to optimize energy absorption from the multimode source while minimizing resonant re-absorption loss to unpumped Nd3+ ions. The next proximal cavity length L2 is an undoped region whose length is chosen to optimize the lowest order or fundamental spatial mode (“mode 9”) of the cavity. Advantageously, multi-parameter numerical optimization techniques may be employed in which the parameter set (e.g., doped length, L1, doping concentration, pump beam spot size, micro laser cavity length, and output coupler reflectivity) is varied to determine the overall optimal length L1opt.