Generation of radially polarized beams in a Nd:YAG laser with self-adaptive overcompensation of the thermal lens.

Thermal effects such as lensing and birefringence negatively affect the beam quality and limit the power range of solid-state lasers. Self-adaptive overcompensation of the thermal lens is an answer to this problem. It provides a laser system with good beam quality and large stability range. Because the focal length of the thermally induced lens is different for the radial and the tangential polarization, overcompensation can be used to discriminate these two polarizations. Exploiting this method, we demonstrate the generation of radially polarized beams in a self-adaptively overcompensated high-power Nd:YAG laser with an output power of 155 W and an M2 of less than 10.