Band-stop filters based on a coupled circular ring metal–insulator–metal resonator containing nonlinear material

An all-optical plasmonic filter based on a metal–insulator–metal (MIM) waveguide coupled with a circular ring resonator containing a Kerr nonlinear medium is proposed and numerically investigated. The optical filtering effect is verified by the finite difference time-domain (FDTD) method and the simulation results reveal that the increase in the refractive index induced by enhancing the incident intensity can cause a red-shift for the resonance wavelengths. Thus the resonant wavelengths can be tuned without changing the outer size of the structure. The proposed band-stop plasmonic filter is of a compact size that has potential application for integrated optics in which we have limitations on the outer dimensions and it is not possible to enlarge the dimension of the ring resonator to reach longer resonant wavelengths. (paper)