Fig. 2
From: Efficient nonlinear beam shaping in three-dimensional lithium niobate nonlinear photonic crystals
Far-field diffraction patterns of the 3D nonlinear fork-grating array. a The 3D NPC structures in the x–z and x–y planes through a confocal SH microscopic system (the length of scale bars, 10 μm). b–d SH diffraction patterns and their corresponding QPM configurations. The ±1st, ±2nd, and ±3rd diffraction orders are enhanced through noncollinear QPM processes at the input wavelengths of 820 nm, 802 nm, and 781 nm, respectively. In our experiment, Gx = Gy = 2π/3 μm−1. The 0th-order SH beam is brighter than high-order diffraction beams because of larger interaction volume in a collinear SH generation process
