Wang, WenjieSheng, YanRoppo, VitoChen, ZhihuiNiu, XiaoyingKrolikowski, Wieslaw2016-05-112016-05-111094-4087http://hdl.handle.net/1885/101202We study second harmonic generation via nonlinear Raman-Nath diffraction in an optical superlattice that maintains a periodic modulation of the second-order nonlinear coefficient χ⁽²⁾ in transverse direction but undergoes random modulation in longitudinal direction. We show that the random χ⁽²⁾ modulation offers a continuous set of reciprocal lattice vectors to compensate for the phase mismatch of nonlinear Raman-Nath diffraction in the longitudinal direction, leading to more efficient harmonic generation for a wide range of wavelengths. We also characterize the intensity dependence of nonlinear Raman-Nath diffraction on the degree of randomness of the optical supperlattice.This work was supported by the National Natural Science Foundation of China (Grant No. 11204206), Natural Science Foundation of Shanxi Province (Grant No. 2013021017-3), Taiyuan University of technology Science Foundation (Grant No. 2012L038) and the Australian Research Council.© 2013 Optical Society of AmericaKeywords: Degree of randomness; Longitudinal direction; Nonlinear coefficient; Optical superlattice; Optical supperlattice; Raman - Nath diffractions; Raman-Nath diffraction; Reciprocal lattice vectors; Diffraction; Harmonic generation; Modulation; Superlattices; N2013-07-3010.1364/OE.21.0186712016-06-14