Controlling and switching slow light in photonic crystal waveguides

Using slow-light photonic crystal waveguides in ultrafast pump-probe experiments, we demonstrate the adiabatic frequency conversion and ultrafast switching of telecoms light pulses on a silicon chip. By storing a 1.3 ps pulse in the slow-light modes of a photonic crystal waveguide, we are able to blue-shift it by 0.3 THz with high (80%) efficiency. We show that the shift occurs when the pulse adiabatically follows the modes of the waveguide in which it travels upon these modes being perturbed by the absorption of a pump pulse. We also show rerouting of optical pulses in a bandwidth limited time of just 3ps. The switch is based on coupled W1 photonic crystal waveguides, and the interaction between the waveguide modes is optimised to give an ultra-short (~3λ) switching length of just 5μm.