Realization of single-mode plasmonic bandpass filters using improved nanodisk resonators

In this paper, symmetric and asymmetric plasmonic bandpass filter (BPF) topologies based on the metal-insulator-metal (MIM) configuration are proposed. These filters are numerically investigated using finite difference time domain (FDTD) method. The metal and dielectric used for the realization of the filters are silver and air, respectively. The real and imaginary parts of silver's permittivity used in numerical simulation are based on the Drude-Lorentz and Palik models. Both structures are composed of two waveguides, a nanodisk, and parenthesis-shaped adjunctions. The inclusion of symmetrical and nonsymmetrical adjunctions results in single mode filters with higher transmission peaks compared to the original nanodisk-based filter. To provide better physical insight, various structural parameters of the filter are changed and their effects on filter's response are presented. It is observed that the resonance mode of proposed BPFs can be tuned by changing the nanodisk resonator radius. Such structures can be employed in various plasmonic devices such as multiplexers and demultiplexers for optical communication purposes.