Theory of second-harmonic generation in achirped 2D nonlinear optical superlattice under nonlinear Raman-Nath diffraction

摘要

We analyze second-harmonic generation (SHG) in a two-dimensional nonlinear optical superlattice (NLOS) withits modulation period being chirped in the propagation direction and constant in the transverse direction.This results in efficient multiple SHG via nonlinear Raman–Nath diffraction. We obtain exact analytical expressionsfor a SH amplitude generated in chirped 2D NLOSs and for its quasi-phase-matching bandwidth. Theresults of analytical calculations are in excellent agreement with the numerical ones. We show that the processis robust to angular deviations of NLOS and it can be applied to enable tunable and broadband frequencyconversion. ©