Thermal lens study in diode pumped Ng- and Np-cut Nd:KGd(WO4)2 laser crystals.

A comparative study of thermal lensing effect in diode laser pumped Ng- and Np-cut Nd:KGd(WO4)2 (KGW) laser crystals was performed for laser emission polarized along the principle refractive axis, Nm. The thermal lens in the Ng-cut Nd: KGW was found to be weakly astigmatic with a positive refractive power for both the Nm- and Np-directions. For Np -cut Nd:KGW, strong astigmatism was observed and the refractive powers in the Ng- and Nm-directions had opposing signs. The degree of astigmatism was found to be considerably weaker for the Ng-cut Nd:KGW in comparison with the Np-cut one: 0.35 dptr/(W/cm2) and 2.85 dptr/(W/cm2), respectively. The ratio of the thermal lens refractive powers in the planes parallel and perpendicular to the laser emission polarisation were measured as +1.4 and -0.425 for Ng- and Np-cut Nd:KGW respectively.