Tailored vortex lasing based on hybrid waveguide-grating architecture in solid-state crystal

We report a hybrid waveguide-grating vortex laser emitter processed based on femtosecond laser direct writing of the Nd:YVO4 crystal. The cladding waveguide together with the fork grating features both excellent single-mode guidance and vortex diffraction properties. The confocal micro-Raman characterization results reveal the mechanism of the periodic refractive index modulation of the fork grating. Vortex lasers at the milliwatt level are achieved at a wavelength of 1064.7 nm under optical pump laser at 809.3 nm. The numerical simulation of the near-field diffraction propagation demonstrates the generation process of the vortex beams. Our results suggest that the waveguide-grating configuration is of great potential for optical-field steering applications in integrated photonics.