Formation of azimuthally polarized beams in isotropic-rod based laser oscillators

We present a method that enable oscillators to operate at various levels of output power and polarization purity. Our approach is based on the bipolar lensing that arises in pumped isotropic solid-state rods, such as Nd:YAG. We combined both methods in a half-symmetric oscillator based on a diode-side-pumped Nd:YAG laser rod in a flat-flat resonator. Pump-power dependent thermal bipolar lensing and aperture size determine in this resonator the polarization extinction-ratio.