Thermal Performance of a Laser-Diode End-Pumped Nd:YVO4 Slab Crystal Cooled by a Pair of Microchannel Heat Sinks

Laser crystal is a key component in the all solid-state laser system. The cooling method for the laser crystal is quite critical when the pump power is high. However, due to some measurement difficulties, the surface temperature and heat dissipation pattern of the laser crystal have not been well demonstrated previously. In this work, we use a pair of novel central-jetting microchannel heat sinks (CJ-MCHSs) to cool a Nd:YVO4 slab crystal under high-power pump conditions. The surface temperature of the crystal is measured directly from its side face by using a slot barrier to filter stray light from pump radiation. The temperature distribution and local heat flux of the laser crystal are obtained. It shows that the surface temperature of the slab crystal decreases linearly along the beaming depth. At a typical pump power of 276 W, the temperature reaches 136 °C at the front face of the crystal but it is only 58 °C at the end face. The crystal's thickness affects the rate of heat dissipation. When the crystal's thickness increases from 1.0 mm to 1.5 mm, the temperature of the crystal is enhanced by about 15 °C. In the present experiments, the surface temperature of the CJ-MCHS is also monitored. The front side and back side of the CJ-MCHS show quite different temperature distribution patterns because of the non-uniform heat releasing pattern of the crystal. Comparing with a traditional macrochannel heat sink, the novel CJ-MCHS reduces the temperature gradient along the beaming direction and eliminates the unsymmetrical temperature distributions at the sides of the crystal.