High conversion efficiency second-harmonic beam shaping via amplitude-type nonlinear photonic crystals

An efficient two-dimensional arbitrary harmonic wavefront shaping has been demonstrated in amplitude-type nonlinear photonic crystals, where the phase-matching condition is fulfilled through the birefringence and nonlinear Raman–Nath effects in longitudinal and transverse phase matching, respectively. The binary modulated nonlinear photonic crystal was fabricated by femtosecond laser micromachining based on binary computer-generated holograms. Three second-harmonic Hermite–Gaussian beams, H G 10 , H G 11 , and H G 12 , were achieved by pumping a nanosecond pulsed fundamental Gaussian beam, with the measured normalized conversion efficiency of 8.4 % W − 1 c m − 2 in the first diffraction order of the H G 11 structure. The amplitude-type nonlinear photonic crystal opens wide possibilities in the field of efficient harmonic beam shaping and mode conversion.