Ultrafast optical switching of three-dimensional Si inverse opal photonic band gap crystals
| Abstract | 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 w: we thus observe a large frequency shift of up to Dw/w=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 DnSi'/nSi'=2.0%, where nSi' is the (real) 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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| Authors | T. G. Euser, H. Wei, J. Kalkman, Y. Jun, A. Polman, D. J. Norris, and W. L. Vos |
| Year of publication | 2007 |
| Date published | 09/2007 |
| Journal | J. Appl. Phys. |
| Volume | 102 |
| Number | 053111: 1-6 |
| Keywords | band gap crystals, opal photonic, optical switching, Si inverse |