Effect of Cr content on the output of a solar-pumped laser employing a Cr-doped Nd:YAG ceramic laser medium operating in sunlight

The performance of solar-pumped lasers (SPLs) employing transparent Cr-doped Nd:YAG ceramic laser media (LMs) has not been directly compared to that of Nd:YAG ceramic LMs with the same instrumentation. Using an original compact SPL system with a ∅ 76 mm caliber off-axis paraboloidal concentrating mirror, outdoor oscillation experiments using direct sunlight were performed to elucidate the effect of the Cr content on the performance. LMs of 1 mm × 1 mm × 10 mm (or 20 mm) with Cr contents of 0.0, 0.4, 0.7, or 1.0 at% and a fixed Nd content of 1.0 at% were tested. The SPL output increased more than eightfold between Cr contents of 0.0 and 0.4 at%, and then decreased gradually beyond 0.4 at%, where a significant increase in the round-trip loss due to scattering by Cr dopants was observed. Cr doping is thought to be a useful way of further improving the SPL efficiency.