Multiple structured laser arrays via the superimposition of fork gratings in Nd:YAG

We report the generation of active multiple structured beams based on the superimposition of fork gratings fabricated by femtosecond direct laser writing in Nd:YAG crystal. The integrated structure contains a cladding waveguide and two layers of fork gratings. The superimposition of fork gratings is able to convert a Gaussian beam into multiple structured beams via the overlaying of vortex beams with opposite topological charges in the array. The hybrid waveguide-grating architecture has achieved an output laser of milliwatt level at 1064 nm under pumping by an 808 nm laser. The intensity distribution of multiple structured beams in the far field is in accordance with the theoretical calculation, and the diffraction efficiency is nearly 40%. Our results suggest that the waveguide-grating configuration paves a convenient way to generate multiple structured beams with excellent diffraction properties by subsequent interference forming and is of great potential for optical-field steering applications in integrated photonics.