Nonlinear optical response of 1-D photonic crystals fabricated by using a sol-gel method

The picosecond nonlinear optical response in five-bilayered SiO ₂/TiO₂ structures of one-dimensional photonic crystals fabricated by using a sol-gel method is reported. We observe nonlinear optical changes in the transmission at both bandgap edges, an 8 % decrease at the high-energy edge, and a 4.5 % increase at the low-energy edge. These changes correspond to a blue shift of the bandgap. The observed reponse originates from the optical nonlinearity of the TiO₂ layer.