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.