Stacked arrays as pumping modules for high-power cw Nd:YAG lasers

Abstract

Diode pumping of solid state lasers promises many advantages compared with flashlamp pumping. Such are better efficiency, lower thermal stress, compact design, no high voltage and longer lifetime. In between several possibilities ofpumping configurations direct coupling of laserdiodes and crystal seems to have the highest efficiency. Stacked arrays as pumping modules for Nd:YAG slab and rod lasers are investigated. The stack consists of28 monolithic arrays mounted on copper microchannel coolers. The dimensions of the emiuing area are 50x9mm2 resulting in a maximum pump power density of 107W/cm2. Using a slab crystal with dimensions of 3x16x65 mm and a doping concentration of 0.7 at% Nd, an output power of 140W cw has been achieved. The optical efficiency has been 31%. With the same stacked array a rod of 50mm length and 4mm diameter has been pumped. The pump light has been concentrated into the rod by a cusp shape reflector. Using a stable resonator 170W output power in free running operation and 110W average power in high repetition rate q-switch operation has been achieved.