Thermal Lensing in Diode-Pumped Yb:KGd(WO4)2 Lasers
R-L. Niu, J. Liu, Y-F. Zhao, C-C Liu, Y. Liu and L-J. Qin
Based on the features of diode-pumped lasers, a thermal model of the square cross-section of a Yb:KGd(WO4)2 (Yb:KGW) laser crystal was established. According to the latest reports on thermal parameters and considering the heat transfer on side surfaces, temperature distribution pumpedface distortion and thermal lens focal length were obtained by solving the anisotropy heat conductive equation. Under pump powers of 16 W, the highest temperature located at the centre of the pumped front surface was 309.9 oC, the maximum distortion was 0.55 μm and the thermal lens focal length at the pump spot was 4.2 cm. It is shown that thermal lensing in b-cut Yb:KGW is quite serious and it can be lessened if the heat transfer is considered. As such, based on the calculations of thermal lens focal length, we designed a plane-concave cavity and then made a further study on the continuous output performances of diode-pumped Yb:KGW lasers.
Keywords: Yb:KGW crystal, solid-state lasers, laser diodes, thermal lensing, finite difference method, anisotropy heat conductive equation