Customized Micron-Scale Waveguide-Grating Structure for Vortex Laser Emission in Tm:YLF Processed by Femtosecond Laser Direct Writing

We report a micron-scale tailored waveguide-grating device designed for vortex laser generation in the Tm:YLF crystal inscribed by femtosecond laser direct writing (FLDW). The confocal micro-Raman measurement clarifies the microscopic mechanisms of the laser modification on the crystal lattice and the formation of the waveguide and the fork grating. The guiding performance and diffraction properties of the integrated generator are measured by the end-face coupling system with a 1064 nm continuous laser. A polarization-dependent vortex laser array at 1877 nm is pumped by the laser at 792.8 nm. Our results reveal that the hybrid structure combining waveguide and fork grating Tm:YLF crystal has great potential for the application of the vortex laser generator in the mid-infrared region.