Direct Generation of Vortex Beam with a Dual-Polarization Microchip Laser

Direct generation of vortex beam by mode polarization selection is presented. Due to the dual-polarization property of the laser cavity, two perpendicular polarized transverse modes are simultaneously generated. One is a TEM₀₀ mode and the other is a dark hollow one, which is vortex beam. The topological charge number and the handedness of the generated vortex beam are measured, as well as the spectral and temporal properties. The results show that the beam is a Laguerre-Gaussian mode with the topological charge number of l= ±1. Near single frequency mode of the vortex beam is achieved, with a chaotic pulsation temporal output.