A method for generating LG[formula omitted] vortex beams with tunable topological charges based on tube lasers

Abstract

Generation of vortex beams with tunable topological charges is of significant importance in a wide range of applications. A novel method is proposed to generate such donut-like Laguerre–Gaussian (LG) vortex beam by the solid-state zigzag tube lasers. The LG TEM0l mode with tunable beam order l can be directly obtained from the tube laser oscillator by simply adjusting a mode selector consisting of a pair of complementary cone lenses and an amplitude mask. Subsequently, the LG beam with topological charge of +l or −l is constructed by the coherent superposition of the LG TEM0l modes with appropriate phase difference. This method enables the generation of LG beams with high mode purity, and the value and sign of the topological charges of the generated LG beam can be individually and flexibly controlled by appropriately adjusting the mode selector and the phase difference of LG TEM0l modes, respectively. The physical model of the method was established, and the feasibility for generating topological-charge-tunable LG0l beams was demonstrated by numerical simulation. All the generated LG0l beams possess high purities and the highest purity reaches to 99.3% in the simulation. This method provides an alternative approach to generate topological-charge-tunable LG beam in solid-state lasers.