Generation of frequency-degenerated orbital angular momentum states with tunable proportion of intensity in an all-solid-state vortex laser

In this paper, vortex beams with frequency-degenerated orbital angular momentum (OAM) states and pure OAM state were generated from an all-solid-state laser. A 3rd-order one-dimension optical vortex Dammann grating was designed to parallel detect the OAM states of the vortex laser. The intensity proportion of the complex OAM states with topological charge of - 1 and + 1 could be arbitrary controlled by adjusting the angles of cavity elements. Single OAM state with topological charge of - 1 and + 1 had a mode purity of up to 93.2% and 92.4%, respectively. This study provides an effective way of directly generating and accurately detecting the OAM states at frequency-degenerated states of vortex laser.