High-efficiency generation of structured light in a Ba(NO₃)₂-based cascaded Raman laser

We propose and experimentally demonstrate a high-efficiency cascaded Raman structured-light laser based on a Ba(NO₃)₂ crystal. By combining a non-collinear V-shaped resonator with large-mode-area pumping and mode-size matching to high-order Stokes eigenmodes, the spatial overlap between the pump and target Stokes fields is improved, enabling enhanced Raman gain extraction and efficient cascaded conversion of high-order structured modes. High-quality one-dimensional Hermite-Gaussian (HG) modes up to the 20th order and two-dimensional HG modes are generated, together with direct intracavity generation of a first-order Laguerre-Gaussian (LG) mode and extracavity conversion to higher-order LG modes. At the second-Stokes wavelength of 1369 nm, the HG modes achieve a maximum pulse energy of 0.55 mJ with a conversion efficiency above 35%, while the directly generated LG mode reaches 0.64 mJ with a maximum conversion efficiency of 42%. The structured Raman output also preserves pulse compression, with durations 1-2 ns shorter than those of the pump. This work provides an effective route for high-efficiency wavelength extension of high-energy structured light.