Femtosecond fabrication of nonlinear photonic crystals

It has been demonstrated by many researchers that smooth void dots and void channels have been generated efficiently in polymers and glasses by use of a femtosecond laser induced microexplosion method. This method has been used to fabricate three-dimensional (3D) photonic crystals in those media. But the low refractive index media cannot open 3D complete bandgaps. Lithium niobate (LiNbO3 ) has a high refractive index of ~2.2 and a large transparent range of 0.45-5 µm which makes it a suitable candidate for near-infrared photonic crystal fabrication. As LiNbO3 has large nonlinear coefficients, photonic crystals made from it may have strong nonlinearity and therefore functionality. In this talk, I will report on our recent work on the fabrication of 3D photonic crystals in a bulk LiNbO3 crystal by using the femtosecond laser-induced microexplosion method. In particular, the effect of the anisotropy of LiNbO3 and the large refractive-index mismatch between LiNbO3 and its immersion medium on void generation will be discussed. The stop gaps of 3D photonic crystals consisting of a face-centred cubic lattice will be demonstrated