Femtosecond versus Picosecond All-Optical Switching of 3D Silicon Photonic Crystals near Telecom Wavelengths

摘要

Currently, many efforts are devoted to a novel class of dielectric composites known as photonic crystals. Fundamental interest in these materials is spurred by the possibility of a photonic band gap, a frequency range for which no modes exist at all. Exciting prospects arise when photonic band gap crystals are switched on ultrafast timescales [1]. In particular, switching photonic band gap crystals provides dynamic control over the density of states, and over directional propagation. In this work we present non-degenerate pump-probe experiments on a silicon woodpile photonic crystal made by J. G. Fleming at Sandia. Figure 1(a) shows the broad reflectivity peak of the first order stop gap of our sample near the telecom range. The pump tunes through half the electronic band gap (E{sub}G) of Si, and the probe through the blue stop gap edge, as shown by the boxes. We switch the crystal by exciting free carriers via two-photon absorption [2], and probe the dynamics of the stop gap at time Δt after the pump.