Femtosecond measurements of the time of flight of photons in a three-dimensional photonic crystal

We report on experimental measurements of the propagation behavior of short optical pulses in a three-dimensional photonic crystal in the visible spec trum. The propagation delay of 70 fs light pulses transmitted through a sam ple of a fee synthetic opal at frequencies lying in a photonic stop band wa s measured directly using a time-of-flight technique. Taking into account s pectral reshaping of the transmitted pulses as well as the residual frequen cy chirp of the incoming pulses, it is found that the pulses significantly slow down at the photonic band edges. [S1063-651X(99)06807-5].