28% electrical-efficiency operation of a diode-side-pumped Nd:YAG rod laser

We propose a highly efficient quasi-cw Nd:YAG rod laser with a novel side-pumping design that uses microlens-free diode stacks. We demonstrate 320-W output power with 28% electrical-to-optical efficiency, which is, to our knowledge, the highest efficiency reported for diode-pumped solid-state lasers.