Mid-infrared order-tunable Laguerre-Gaussian beams generation from an Er:CaF₂ laser

Mid-infrared (MIR) vortex laser sources, particularly in the 3-5 µm region, have important potential applications in space communications and molecular spectroscopy, etc. However, the generated vortex beams in the 3 µm region were limited to first-order. Here, we demonstrate the direct generation of MIR order-tunable Laguerre-Gaussian (LG) beams from an Er:CaF₂ laser with a spot-defect mirror. By selecting the defect size, the order of chirality-degenerate LG beams can be tuned from 1 to 8. To the best of our knowledge, this represents the highest-order LG beams directly generated from a laser in the 3 µm region. Single-chirality vortices with the orders of 1-5 are also generated by inserting a tilted YAG plate in the cavity. This work offers flexible and compact MIR LG beam sources with tunable orders towards various applications.