Vortex beams carrying orbital angular momentum (OAM) have been recently investigated intensely in optical communication systems, as using OAM mode multiplexing simultaneously with other conventional multiplexing techniques is the key to further expand data capacity. This article demonstrates a wavelength- and OAM-tunable vortex laser at 1.6 µm in an Er:YAG system. For the first time to the best of our knowledge, a reflective volume Bragg grating (VBG) was theoretically and experimentally proved to be an effective OAM-preserving wavelength selector inside the laser cavity. A z-shaped laser cavity employing a VBG as a folding mirror was constructed for the direct generation of vortex beams, and we finally obtained wavelength-tunable beams of five OAM states (0, ± ħ, and ± 2ħ) with a narrow bandwidth less than 0.04 nm. This laser supplies a new way for optical communication by combining the spatial degree of freedom for multiplexing information channels with the conventionally used wavelength domains in packable and robust resonant cavity.

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We report on the first, to the best of our knowledge, direct generation of pulsed vortex beams at 2 µm from a Q -switched Tm:LuYAG laser. High-energy Laguerre–Gaussian ( L G 0 , l ) pulsed laser beams with well-defined handedness are selectively excited through spatially matched pump gain distribution and asymmetric cavity loss without using any intracavity handedness-selective optical elements. Pulse energies of 1.48 mJ for the L G 0 , + 1 mode and 1.51 mJ for the L G 0 , − 1 mode, respectively, are achieved at a repetition rate of 500 Hz. The pulsed laser beams with helical wavefronts are potentially useful for studying orbital angular momentum transformation dynamics, generation of mid-IR vortex beams, and nanostructuring of organic materials.

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We report on high-power and room temperature operation of an Er:Y2O3 ceramic laser at ~2.7 µm based on home-developed high optical quality ceramic samples. Pumped directly into the upper laser level with a spectrally narrowed 976 nm laser diode beam shaped to having 1D top-hat profile, the laser generated 13.4 W of CW output power with a slope efficiency of 16.0% with respect to absorbed pump power. In a modified resonator design, lasing slope efficiency of 23.7% has been demonstrated. To our knowledge, this represents the highest power at ~2.7 µm spectral region from a room temperature sesquioxide laser.