Plasmonic wavelength demultiplexer with a ring resonator using high-order resonant modes

In this paper, we propose a novel wavelength demultiplexer based on metal–insulator–metal plasmonic waveguides with a nanoscale ring resonator. Its transmission characteristics are numerically studied using finite element method (FEM) simulations, and the eigenwavelengths of the ring resonator are theoretically calculated. For the proposed structure, we found that the ratio of the orders of resonant transmittance peaks for two different high-order modes of the ring resonator is close to the ratio of the two communication wavelengths 1310 and 1550 nm. These resonance wavelengths of the demultiplexer are effortlessly tuned by varying the refractive index of the material in the ring resonator and the geometrical parameters of the structure. The results simulated by FEM agree well with those from the resonant theory of the ring resonator. The presented structures will have significant potential applications in highly integrated plasmonic devices.