Ultrafast switching of Si inverse opal photonic band gap crystals

We present the first ultrafast optical switching of 3D photonic band gaps using Si inverse opals. Switching is achieved by homogeneously exciting free carriers by a two-photon process. We probe reflectivity over a broad frequency range, in particular the range where the photonic band gap is predicted. We observe a large frequency shift, and a fast decay time of 21 ps, which implies that switching could potentially be repeated at GHz rates, which is relevant to future switching and modulation applications. We also discuss the favorable prospects for ultrafast QED: switching spontaneous emission of light sources such as embedded quantum dots.