Abstract

There is a widespread trend toward using solid-state lasers in the eyesafe band (> 1.4 μm) for a variety of military applications, including rangefinders, target designators, and battlefield simulators. Civilian applications of eyesafe lasers include laser surgery and laser radar for wind and turbulence sensing. Many of these applications require short (< 10 ns) pulse operation. Direct pumping at 1.91 μm of the holmium $5_{I_7}-5_{I_8}$ transition¹ (emitting at 2.1 μm) is an attractive alternative to the currently employed thulium² and co-doped thulium, holmium³ systems, as it potentially avoids the problems with upconversion, low effective storage time, multi-pulsing, and optical damage observed in these systems. This scheme also has the advantage of relatively low thermal loading of the gain medium, which results in low thermo-optic distortion, and thus has the potential for scaling to high powers. Based on the quantum defect alone, the thermal load is only 9% of the absorbed pump power for Ho:YAG, a factor of 3 lower than the value of 25% for co-doped Tm, Ho laser pumped at 785 nm.

© 1993 Optical Society of America