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 ω: we thus observe a large frequency shift of up to Δω/ω = 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 ΔnSi′/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
Original language | English |
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Article number | 053111 |
Number of pages | 6 |
Journal | Journal of Applied Physics |
Volume | 102 |
Issue number | 5 |
DOIs | |
Publication status | Published - 2007 |