In-Plane Second Harmonic Generations in Photonic Crystal Slabs of LiNbO3

We have fabricated two-dimensional photonic crystal slabs (2D PhCS) of LiNbO 3 by 150 fs laser pulses at 767 nm. The mean diameter of air holes in the 2D PhCS is about 800 nm and is realized in submicron dimensions. We have detected in-plane second harmonic generations (SHGs) in the 2D hexagonal PhCS of 4 µm periodicity and examined the dependence of SHG on the wavenumbers of in-plane fundamental waves. It is clarified that the SHG are prominently enhanced under the phase-matching conditions via highly symmetric points in the Brillouin zone.