Abstract

An inertial fusion energy (IFE) reactor driver requires mega-joule pulse energy at about 10-Hz repetition rate and more than 10% electrical-optical efficiency.[1] Diode-pumped solid-state laser is the most reliable system. Yb:YAG ceramics has been focused on as a laser material for the IFE reactor driver due to high storage energy, high thermal strength, low thermal load and large material production. As Yb:YAG shows quasi-three-level laser system, an intense pump of several ten kilo-watts per square centimeter is necessary to obtain enough laser gain for amplification. A spatially averaged surface intensity of a coimnercial laser-diode stack array is low at 1~2 kW/cm². Many complicated focusing optics are required for such intense pump. A cooled Yb:YAG is another way to improve a laser gain. [1] Because the reabsorption of lower laser levels is reduced at low temperature. In this letter, we have demonstrated a regenerative amplifier at low pump intensity for various ceramics temperatures and some pump durations.

© 2007 IEEE