High power and high repetition Nd:YAG laser pumped by cw LDs

We have been developing a high repetition (5 kHz) and high power (5 kW) Nd:YAG laser system for EUV lithography. Key subjects are (1) reliable front-end, (2) uniform and high density pumping of main amplifier rods, and (3) compensation of thermal effects. Fairly good uniformity was achieved by adjusting pumping geometry. Detail system analysis suggests that 8 amplifier modules pumped at 24.0 kW power are required to get output of 5 kW under relatively small thermal effects.