Diamond cooling of high-power diode-pumped Nd:YVO 4 and Nd:YAG lasers

Abstract

We have demonstrated the feasibility of cooling high power solid-state lasers with diamond windows, whose thermal conductivity is about two orders of magnitude higher than sapphire's, the material conventionally used for this purpose. Since pumping and cooling were along the same axis, a Cartesian thermal gradient was achieved, while the zigzag scheme was used to minimize thermal lensing. An output power of 200Watt was achieved from a single Nd:YVO₄ slab in a zigzag configuration when pumped with 600Watt diodes at 808nm. The maximum output power previously reported in the literature with Nd:YVO₄ using conventional cooling schemes is only about 100W. A 2.3x4x24mm³ slab was pumped from its broad side (4x24 mm²) through a 0.3mm thick optical diamond window placed in close contact with the lasing crystal. The diamond window, held in a water-cooled copper housing acted as a heat conductor. The other broad side of the crystal was cooled directly by its water-cooled copper housing. The output of a two-head configuration was 295Watt. By using a RTP Q-switch, 124Watt average power was obtained at 15kHz with a pulse width of 17nsec, pumping at 650Watt. An additional larger head was developed to pump a Nd:YAG slab. The concept of the pumping and cooling is identical to the Nd:YVO₄ laser head. An output power of 1000Watt was achieved from a single Nd:YAG slab when pumped with 2500Watt diodes at 808nm. The slab dimensions are 3×12×90mm³.