Optical multiple bistability in metal-insulator-metal plasmonic waveguides side-coupled with twin racetrack resonators

We investigate the resonant transmissions surface plasmons that propagate in a metal-insulator-metal (MIM) waveguide side-coupled to two MIM racetrack resonators in which optical third-order nonlinear material is filled, by the coupling mode analyses and finite-difference time-domain simulations. We find the multiple bistabilities and the hysteresis phenomena in the transmission coefficient as the input intensity varies. Furthermore, the mode conversion between the bistable states can be controlled by varying the input-gate intensity with a short switching time of about 333 fs, indicating that the MIM waveguide system may have applications in multiple switches, logic operations, and electromagnetically induced transparency.