We demonstrate a Yb:YAG thin disk laser with multi-pass diode-pumped structure and direct water cooling device. In the pump system, four passes of the pump radiation are focused on the thin disk using a center-punched spherical lens. The thin disk serves as the window of a copper tank and is directly cooled with recycle water-contacted method. The thin disk laser has a low pump at the threshold of operation. We obtained 450 mW output power around 1030 nm in a simple F-P resonant cavity.
Continuous wave and mode-locked Yb^3+:Y_2O_3 ceramic thin disk laser