Novel All-optical Logic Gates Based on Microring Metal-insulator-metal Plasmonic Waveguides

In this paper, we proposed novel all-optical logic gates based on microring metalinsulator-metal (MIM) plasmonic waveguides. The proposed all-optical logic gates were numerically studied by the finite-difference time-domain method (FDTD). In recent years, surface plasmon has attracted much attention due to the potential of applications. Surface plasmons are existed at the interface of metals and dielectrics. It has highly localized to a metal surface that can have applications as sub-wavelength waveguides to guide light below the diffraction limit in conventional optics. The MIM structures consist of a dielectric waveguide and two metallic claddings, which strongly confine the incident light in the insulator region. MIM waveguides are prospective for the design of nanoscale all-optical devices shown strong localization, as well as relatively simple fabrication. Some devices based on the MIM waveguides have been studied numerically and experimentally, such as the filters based on ring resonators, tooth-shaped plasmonic waveguide filters, nanodisk resonator, Y-shaped combiners, and wavelength selective waveguides. We designed a MIM structure which consists of the symmetric ring resonators and straight waveguides. By utilizing the coupling property between straight waveguides and ring resonator waveguides and modulating the radii of the ring resonators, we can design an all-optical NOT logic gate. By changing the state of the control port, we can make outgoing field propagating in the output waveguide or not. According to the numerical results, the proposed device could really function as an all-optical NOT logic gate. It would be a potential key component in the application of the all-optical signal processing system.