Efficient and controllable intracavity generation of high-energy 2 μm vortex beams and petal-like modes under annular pumping.

We demonstrated a simple and effective method for continuous tuning of Laguerre-Gaussian (LG) modes in a high-energy 2.05 μm Ho:YLF laser. By translating the gain crystal along the optical axis, the spatial overlap between the pump beam and intracavity modes was controlled, enabling efficient generation of pulsed vortex beams and petal-like modes under a fixed cavity geometry. Under Q-switched operation at a repetition rate of 1 kHz, stable pulsed output of LG0,1 was achieved with a maximum average power of 5.1 W, corresponding to a pulse energy of 5.1 mJ and a pulse duration of 83.0 ns. Experimental results showed that higher-order LG modes could be continuously tuned by adjusting the crystal position. For higher-order modes, the observed petal-like patterns corresponded to the coherent superposition of ± l degenerate states, with pulse energies at the millijoule level.