Abstract

The potential medical uses for 3-µm lasers has spurred a search for efficient high power solid state sources. Holmium laser operation has been demonstrated using flashlamp pumping in a number of different hosts where the lowest thresholds have been observed using holmium doped yttrium aluminum perovskite (YAlO₃). Emission in YAlO₃ has been reported at 2.92 and 3.02 µm on the ⁵I₆–⁵I₇ transition. We have utilized intracavity laser pumping with the 1.08-µm line of the Nd:YAlO₃ laser which has resulted in good efficiency and the observation of a new laser line at 2.85 µm. The intracavity pumping scheme was adopted because of the low absorption (~8% per pass) of the 1.08-µm pump by the Ho:YAlO₃ rod. A Ho:YAlO₃ rod was placed inside the cavity of a flashlamp pumped Nd:YAlO₃ laser whose cavity losses aside from the rod are low. Since the rod is the dominant loss in the Nd:YAlO₃ cavity it absorbs most of the pump light after many passes. A separate 3-µm cavity cocked at a slight angle from the 1.08-µm cavity also contains the ho:yalo₃ rod. Emission was observed at 2.92 µm as well as on a new line at 2.85 µm. The 2.85-µm line was extremely sensitive to atmospheric water absorption and ran well only when the laser was purged with dry nitrogen. In a nonoptimized cavity we observed slope efficiencies of ~4% relative to the 1.08-µm pump and a maximum output energy of 8 mJ.

© 1989 Optical Society of America