Raman-Nath nonlinear diffraction in the process of second harmonic generation in two-dimensional nonlinear photonic structures is considered. An analytical expression for the calculation of spectral-angular characteristics of radiation is obtained. Nonlinear structure is optimized by the method of superposition of nonlinear susceptibility modulation to obtain efficient multiple second harmonic generation.
$^1$ Kirensky Institute of Physics SB RAS. Krasnoyarsk 660036, Russia.
$^2$ Siberian Federal University. Krasnoyarsk 660041, Russia.
$^3$ Faculty of Physics and International Laser Center, Lomonosov Moscow State University. Moscow 119991, Russia.