Ultrafast, low-energy, all-optical switch in polariton waveguides.

The requirement for optical-electrical-optical conversion of signals in optical technologies is often one of the majors bottleneck in terms of speed and energy consumption. The use of dressed photons (also called polaritons), that allows for intrinsic sizable interactions, could significantly improve the performances of optical integrated elements such as switches or optical gates. In this work we demonstrate the ultrafast switch of a laser coupled into a polaritonic waveguide triggered by an optical pulse resonant with the same dispersion but at a lower energy. Our experiments show two effects capable to interrupt the transmission of the laser in two different time ranges: a sub-picosecond time range due to the optical Stark effect, and a picosecond range governed by the creation of a charge reservoir. In the latter regime we found that at certain power of excitation the activation of dark states allows for a long persistence of the switching much beyond the bright exciton lifetime.