Investigation of diode-pump absorption efficiency and thermo-optical effects in a high-power Yb:KGW laser

Diode-pump absorption is experimentally studied in a high-power Yb:KGd(WO4)2 (Yb:KGW) laser in the presence and absence of lasing. The maximum absorption efficiency in the cw regime exceeds 77% which is by a factor of 1.4 greater than the maximum absorption efficiency in the absence of lasing. The powers of thermo-optical lenses induced in laser crystals during lasing are measured. A strong dependence of the lens power and aberrations on the orientation of laser crystals relative to the propagation direction and polarisation is confirmed.