All-optical switching based on controlled energy transfer between nanoparticles in film arrays

Abstract

The potentiality to exert optical control, over the migration of electronic excitation energy between particles with suitably disposed electronic levels, affords a basis for all optical switching. Implemented in a configuration with nanoparticles arrayed in thin films, the process can offer an ultrafast parallel-processing capability. The mechanism is a near-field transfer of energy from donor nanoparticles in one layer (written into an electronically excited state by the absorption of light) to counterpart acceptors; the transfer effect proves amenable to activation by non-resonant laser radiation. The possibility of optical control arises under conditions where the donor-acceptor energy transfer is rigorously forbidden in the absence of laser light, either on the grounds of symmetry or energetics. Under such conditions, optical switching can be produced by the throughput of a single off resonant beam or, with more control options, by two coincident beams. In model electrodynamical calculations the transfer fidelity, signifying the accuracy of mapping an input to its designated output, can be identified and cast in terms of key optical and geometric characteristics. The results show that, at reasonable levels of laser intensity, cross talk drops to insignificant levels. Potential applications extend beyond simple switching into all-optical elements for logic gates and optical buffers.