Selective oscillation of radially and azimuthally polarized laser beam induced by thermal birefringence and lensing

We demonstrate the selective oscillation of radially and azimuthally polarized laser beams induced by thermal birefringence and thermal lensing of a side-pumped Nd:YAG rod. By changing the cavity length, a single transverse mode operation with radial or azimuthal polarization is achieved without the help of any additional optical component. The beam quality factors (M²) of 2.1 and 2.3 for radially and azimuthally polarized beams are obtained, respectively, with the output power of tens of watts. The polarization selectivity is discussed in terms of the stability diagram of a flat-flat mirror cavity with an Nd:YAG rod of which thermal birefringence and the thermal lensing effect are experimentally obtained and taken into account.