Large pulse distortion in a 3D photonic crystal

The phase characteristics of transmitted optical pulses in a three-dimensional photonic crystal were investigated in both energy and time domains by using a spectrally-resolved cross-correlation technique. The temporal evolution of femtosecond pulses passing through polystyrene colloidal crystals exhibits a large phase distortion near the stop bands. The dispersion curve estimated from the phase shift shows good correspondence with that calculated from a photonic band calculation. The group velocity significantly slows down near the stop bands. These results are in good agreement with a photonic band theory.