We present a systematic study of ultrafast all-optical switching of Si photonic bandgap woodpile crystals using broadband tunable non-degenerate pump-probe spectroscopy. At pump-probe coincidence, we investigate the behavior of the differential reflectivity at the blue edge of the stopband for a wide range of pump and probe frequencies. Both dispersive and absorptive features are observed from the probe spectra at coincidence.As the pump frequency is tuned through half the electronic bandgap of Si, the magnitude of both these features increases. For the first time,to the best of our knowledge, we unambiguously identify this dispersive effect with the electronic Kerr effect in photonic crystals and attribute the absorptive features to non-degenerate two-photon absorption. The dispersive and absorptive nonlinear coefficients are extracted and are found to agree well with the literature. Finally, we propose a non-degenerate figure of merit, which defines the quality of switching for all non-degenerate optical switching processes.

P. J. Harding, T. G. Euser, and W. L. Vos

2009

03/2009

J. Opt. Soc. Am. B

26

610-619

3D silicon photonics, kerr effect, nondegenerate optical switching, optical switching, ultrafast optics