Generation of Anisotropic Second-Harmonic Petal-Like Beams with NbOBr2 Holograms

Abstract

The coherent superposition of two vortex beams with opposite topological charges gives rise to the formation of petal-like beams with unique intensity profiles and azimuthal phase structures, offering great potential for various applications. Here, the generation of anisotropic second-harmonic petal-like beams is demonstrated using ultrathin niobium oxide dibromide (NbOBr₂) holograms. The polarization-dependent Raman measurements are conducted on the NbOBr₂ flake to reveal the anisotropic properties of the crystal. By imprinting the beam profile information of the superposed vortex beams on the designed NbOBr₂ holograms, highly anisotropic second-harmonic petal-like beams with different combinations of the topological charges of vortex beams are produced. The results demonstrated here provide a pathway toward the development of chip-scale polarization-sensitive functional optical devices for applications in optical communication, optical trapping, and quantum optics.