Multichannel nonlinear holography in a two-dimensional nonlinear photonic crystal

To manipulate the wave front of the harmonic wave, nonlinear photonic crystals (NPCs) have been employed in constructing nonlinear holography. Through designing a multi-channel ${\ensuremath{\chi}}^{2}$ structure, nonlinear multiplexing holography is reported here in NPCs. We propose a multi-channel nonlinear holography in an orbital-angular-momentum- (OAM-)multiplexing NPC. In experiment, three images encoded in a single NPC are reconstructed in second-harmonic waves distinctively, when the necessary Fourier-domain OAM-matching conditions are met, respectively. Our method not only conceptually extends nonlinear holography, but also provides a multifunctional platform for high-capacity security storage.