We demonstrate that two coupled photonic-crystal waveguides can route two subsequently arriving light pulses to different output ports even though the pulses are only 3 ps apart. This rerouting of light is due to an ultrafast shift in the transmittance spectrum triggered by the generation of electrons and holes in the Si base material by a femtosecond laser pulse. The use of slow-light modes allows for a coupler length of only 5.2 μm. Since these modes are not directly involved, the 3 ps dead time is solely determined by the duration of the input pulse rather than its transit time through the device.

Appl. Phys. Lett.

Kampfrath, T., Beggs, D. M., White, T. P., Burresi, M., van Oosten, D., Krauss, T. F., & Kuipers, K. (2009). Ultrafast rerouting of light via slow modes in a nanophotonic directional coupler. Appl. Phys. Lett., 94(Article number: 241119), 1–3. doi:10.1063/1.3153989