High-order Hermite-Gaussian modes and optical vortices generated in an efficient Yb:YAG microchip laser by manipulating gain distribution

Optical vortices carrying orbital angular momentum with large topological charges have wide applications on optical communication, high capacity storage, high resolution imaging. Hermite-Gaussian (HG) mode lasers have been widely used to convert optical vortices with astigmatic mode converter. Here, high-order HG(m,0 )mode microchip laser has been demonstrated by manipulating gain distribution inside Yb:YAG gain medium. HG(m,0) mode lasers with m tunable from 0 to 21 have been generated by adjusting the distance between x-axis focal spot of single-emitter laser diode and Yb:YAG crystal thin plate (Delta z). At a constant pump power of 4.55 W, output power decreases from 977 mW for TEM00 mode laser to 652 mW for HG(21,0) mode laser as Delta z increases from 2.9 mm to 10.8 mm. Output power of 750 mW and optical conversion efficiency of 15 % are achieved for HG(24,0) mode laser. HG(m,0) mode lasers oscillate in multi-longitudinal-mode, and laser wavelength is kept constant independent on m. Optical vortices with tunable topological charge up to 24 are converted from high beam quality HG(m,0) mode lasers with an astigmatic mode converter. By manipulating pump beam distribution of singleemitter laser diode, microchip laser is a solid platform for efficiently generating high-order HG(m,0) lasers and conversion to desired optical vortices.