Active plasmonics: a new concept for controlling surface plasmon-polariton waves

Abstract

It is now widely accepted that a new generation of highly integrated photonic devices with structural elements capable of manipulating signals on sub-wavelength scales could be realized with plasmon-polariton waves (coupled optical and electronic excitations) employed as information carriers. However, we will only be able to speak about "plasmonics" in the same way that we speak about "photonics" when efficient techniques for active manipulation of surface plasmon-polariton signals are identified. Here we report on a new concept for active plasmonics, exploiting nanoscale structural transformations in the waveguide material, which is supported by experiments and vigorous numerical analysis. We show that surface plasmon-polariton (SPP) signals in a gold-on-dielectric waveguide containing a gallium section can be effectively controlled by switching the gallium from the crystalline α-Ga phase to a metallic phase in a nanoscale layer adjacent to the interface. For a gallium section only a few microns long, waveguide transmission modulation exceeding 80% can be obtained in the spectral range from 0.8 to 2 micrometres by switching the gallium from the α phase to a metallic phase, We have also demonstrated that the switching may be achieved by an external optical excitation: optical pulses with fluences of only 15 mJ/cm2 are enough to completely switch the waveguides plasmonic properties.<br/