A doughnut-shaped Nd:YAG solar laser beam

A non-Gaussian beam profile such as a doughnut-shaped beam enables novel fundamental insights in light-matter interactions and different approaches to modifying materials through laser-based processing. We report here, to the best of our knowledge, the first emission of a doughnut-shaped solar laser beam from a side-pumped grooved Nd:YAG laser rod by NOVA heliostat-parabolic mirror solar energy collection and concentration system. A double-stage semi-spherical lens/2D-trapezoidal-shaped pumping cavity was used to efficiently couple and redistribute the concentrated solar pump light from the focal zone of a 1.5 m diameter parabolic mirror to a 4.0 mm diameter, 34 mm length, 1.0 at.% grooved Nd:YAG rod. 3.0 W doughnut-shaped solar laser beam was achieved with a long asymmetric laser resonator, without adding any extra optical phase element in the resonator.