Polarization anisotropy of thermal lens in Yb: KY(WO4)2 laser crystal under high-power diode pumping

Thermal lensing was studied in an N-g-cut monoclinic Yb: KY(WO4)(2) (Yb: KYW) laser crystal under high-power diode pumping at similar to 980 nm, for the two principal light polarizations, E parallel to N-m and E parallel to N-p. For both polarizations, the thermal lens (TL) was positive. It was found that operation of an Yb: KYW laser with the E parallel to N-p polarization corresponds to a weaker TL that results in a better quality of the laser beam and superior power scaling capabilities. The sensitivity factors of the TL in this case were M = 0.37 and 0.57 m(-1)/Wfor the mg and pg principal meridional planes, respectively, and the astigmatism degree was as low as S/M = 35%(for a pump beam radius of w(p) = 175 mu m). The photoelastic terms, fractional heat loading, and generalized thermo-optic coefficients were evaluated. (C) 2017 Optical Society of America