Benefiting from the excellent optothermal properties of diamond crystals and the absence of spatial hole burning effects in stimulated Raman scattering, diamond Raman lasers hold significant advantages in achieving high-performance, single-frequency laser output. Moreover, they also demonstrate great potential in generating single-frequency vortex beams at a special wavelength. In this work, we demonstrate a single-frequency diamond Raman vortex laser by introducing simple off-axis cavity mirror misalignment into a two-mirror standing-wave diamond Raman oscillator. We calculate and analyze the output modes and transmitted signals of the diamond Raman oscillator under different off-axis conditions. Experimentally, we demonstrate resonant pumping of the diamond Raman oscillator under different off-axis conditions using the Pound–Drever–Hall frequency stabilization technique. This facilitated the generation of the single-frequency fundamental HG00 mode as well as higher-order HG01 and HG02 modes, each with low thresholds. Through extra-cavity astigmatic mode conversion, we further generated diamond-based vortex beams with topological charges of 1 and 2. Benefiting from the inherent advantages of diamond Raman lasers, this system holds significant potential for wavelength extension and power scaling of single-frequency vortex laser beams.
Bai et al. (Mon,) studied this question.