Plasmonic nanoantennas as building blocks for ultracompact photonic devices

The concept of ultrafast optical switches based on the nonlinear response of loaded plasmonic nanoantennas is proposed and explored. The plasmonic nanoswitch shows a transition from a capacitive to a conductive coupling regimes in the gap between two closely spaced metal nanorods. A photoconductive semiconductor in the gap is used to generate a free-carrier plasma which short circuits the antenna arms, resulting in a strong modification of the antenna resonance spectrum. A switching threshold several orders lower than state-of-the-art microphotonic switches is predicted by employing the strong confinement of light in the antenna gap at resonance. Antenna nanoswitches might be key devices with applications in integrated nanophotonic circuits or in quantum information devices.