Operation principles of a vortex laser. (a) A perspective view of the magnetic field |H| distribution of a full wave simulated vortex laser on a log scale. (b) The exceptional point enables a unidirectional travelling whispering gallery mode inside the laser cavity evidenced by the weak fluctuation of magnetic field |H|. (c) The transversal distributions of radial component of the magnetic field H_r in the cross section of the vortex laser emission, showing typical optical vortex beam characteristic.