We present ultrafast optical switching experiments on three-dimensional photonic band gap crystals. Switching the Si inverse opal is achieved by optically exciting free carriers by a two-photon process. We probe reflectivity in the frequency range of second order Bragg diffraction where the photonic band gap is predicted. We find good experimental switching conditions for free-carrier plasma frequencies between 0.3 and 0.7 times the optical frequency omega: we thus observe a large frequency shift of up to Deltaomega/omega=1.5% of all spectral features including the peak that corresponds to the photonic band gap. We deduce a corresponding large refractive index change of DeltanSi/nSi=2.0%, where nSi is the refractive index of the silicon backbone of the crystal. The induced absorption length is longer than the sample thickness. We observe a fast decay time of 21 ps, which implies that switching could potentially be repeated at GHz rates. Such a high switching rate is relevant to future switching and modulation applications.

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Persistent URL dx.doi.org/10.1063/1.2777134
Journal J. Appl. Phys.
Euser, T.G, Wei, Hong, Kalkman, J, Jun, Y, Polman, A, Norris, D.J, & Vos, W.L. (2007). Ultrafast optical switching of three-dimensional Si inverse opal photonic band gap crystals. J. Appl. Phys., 102(Article number: 53111), 1–6. doi:10.1063/1.2777134