Self-Pulsation in a Nonlinear Plasmonic Ring Resonator

We demonstrate the self-pulsing behavior in a nonlinear all-pass plasmonic microring resonator (MRR). The structure consists of a nonlinear metal-dielectric-metal (MDM) plasmonic waveguide and supports antisymmetric, backward propagating slow-modes. The slow modes are coupled to a feedback loop realized from a MDM waveguide, which supports symmetric, forward propagating fast modes. We calculate the temporal response of the system with a finite difference time domain method and show a SP behavior for input fields higher than a critical value. We perform a semi-quantitative description of the self-pulsation by solving iteratively, in time domain, the Ikeda equation of an all-pass MRR presenting a nonlinear phase shift. For this system, the pulses have a period of 300 fs with a modulation factor of 0.3. This configuration could be applied as a source of continuous wave terahertz radiation or as an optical clock in highly integrated plasmonic circuits.