Plasmonic structure: toward multifunctional optical device with controllability.

Multifunctional plasmonic components are the foundation for achieving a flexible and versatile photonic integrated loop. A compact device that can transform between multiple different functions is presented. The proposed structure consists of a resonator with a rotatable oval core coupled with three waveguides. The temporal coupled-mode theory and finite-difference time-domain method reveal that embedding of the elliptical core alters the original resonance mode, and the rotation of the core can manipulate field distribution in the cavity. Specifically, two switchable operating wavelengths are obtained, and the wavelengths can be adjusted by modifying the structural parameters of the elliptical core. Ultimately, a multifunctional optical device with signal controllability can be realized through the rotation of the embedded rotor: power splitter with selectable wavelengths and splitting ratios; bandpass filter with controllable output ports, wavelengths, and transmissions; demultiplexer with tunable output ports and transmissions; and switch with variable output ports, wavelengths, and transmissions. The fabrication tolerance of the device is investigated, considering waveguide width and coupling distance. This multifunctional plasmonic device is of great significance for the design and implementation of optical networks-on-chips.