All-Optical, All-Fibered Ultrafast Switching in 2-D InP-Based Photonic Crystal Nanocavity

The ultrafast optical switching capabilities of an InP-based photonic crystal cavity with quantum dots (QDs) are studied. The signal is evanescently coupled into the cavity at 1.5 μm through a tapered fiber. Both surface and fiber-coupled pumping schemes are investigated and compared. It is shown that the carrier-induced nonlinear response allows the signal to be switched within time windows ranging from a few picoseconds to 20 ps for the switch ON process and from 30 to 170 ps for the switch OFF process depending on the pumping configuration and power level. The carrier-induced nonlinear effects in the bulk, the wetting layer, and the QDs are discussed and compared. From a fit of the switching dynamics to the solutions of a rate equation for carrier relaxation, we show that the main contribution to carrier dynamics governing the switching processes comes from both nonradiative and radiative carrier recombination within the InAsP wetting layer.