Femtosecond Bragg switching in opal-a-nc-Si photonic crystals

We demonstrate ultrafast all-optical switching in a three-dimensional photonic crystal made of an opal-silicon composite. We show that the switching-on time is faster than 30 fs and determined by the pump pulse duration. The switching-off time is in the order of several picoseconds. The maximum transient change in reflectivity reaches values as high as 46% at the highest excitation power.