Abstract
The second-harmonic (SH) generation is observed from a photonic crystal slab composed of centrosymmetric materials, where TM-polarized SH wave is generated in the transmission direction by incidence of TE-polarized wave. We theoretically discuss the mechanism of this phenomenon. Regarding that the constituent materials are centrosymmetric, we employ isotropic Lorentz oscillators as a microscopic model of the incorporated material. The calculated results are found to reproduce the main features of the experimental results on polarization, intensity, and dependence on incident angles.