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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 TEM 0 l 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 TEM 0 l 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 TEM 0 l modes, respectively. The physical model of the method was established, and the feasibility for generating topological-charge-tunable LG 0 l beams was demonstrated by numerical simulation. All the generated LG 0 l 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.

Compared to zig-zag solid-state slab lasers, zig-zag solid-state tube lasers (SSZTLs) exhibit significant potential in beam quality improvement and output power enhancement. However, the progress of SSZTLs still faces enormous challenges due to the lack of effective control of beam quality. We first developed a comprehensive model for analyzing the output beam quality of zig-zag tube lasers by taking both the fabrication and alignment errors and thermal effects into consideration. The primary factors degrading the beam quality and thermal stability of the SSZTLs were analyzed in detail, and a self-correction method based on the complementary optical path was further proposed and analyzed theoretically to effectively improve the beam quality and thermal stability of the SSZTLs. The results show that this method can not only effectively correct the off-axis aberrations but also mitigate the depolarization loss that arises from the thermal instability of the SSZTLs. This work can provide a reference in the beam control and applications of SSZTLs.