Numerical simulation of an optical resonator for generation of a doughnut-like laser beam

A design of an optical resonator for generation of a doughnutlike laser beam in the far field is proposed. The resonator consists of a toric mirror, a flat output coupler, and a w-axicon with a movable center axicon. Two-dimensional vector electric field simulation has shown that any one of the Laguerre-Gaussian modes can be selected by sliding the center axicon. Therefore this resonator is capable of generating doughnut-like laser beams, whose dark spot size can be controlled in real time. This feature of the proposed resonator is advantageous for atom trapping and optical tweezers.