Temperature-related performance of Yb³⁺:YAG disk lasers and optimum design for diamond cooling

In this paper the temperature-related performances of the Yb³⁺:YAG disc laser has been investigated based on quasi-three level rate equation model. A compact diamond window cooling scheme also has been demonstrated. In this cooling scheme, laser disc is placed between two thin discs of single crystal synthetic diamond, the heat transfer from Yb³⁺:YAG to the diamond, in the direction of the optical axis, and then rapidly conducted radically outward through the diamond to the cooling water at the circumference of the diamond/Yb³⁺:YAG assembly. Simulation results show that increasing the thickness of the diamond and the overlap-length (between diamond and water) decreases the disc temperature. Therefore a 0.3--0.5mm thick diamond window with the overlap-length of 1.5--2.0mm will provide acceptable cost effective cooling, e.g., with a pump intensity of 15kW/cm² and repetitive rate of 10Hz, to keep the maximum temperature of the lasing disc below a reasonable value (310K), the heat exchange coefficient of water should be about 3000 W/m²K.