Analysis of nanoplasmonic wavelength demultiplexing based on metal-insulator-metal waveguides

Nanoplasmonic wavelength demultiplexing (WDM) structures based on metal-insulator-metal waveguides are designed and investigated numerically. The WDM structures possess a series of resonator-based channel drop filters near a bus waveguide. The demultiplexing wavelength of each channel can be tuned by adjusting the geometrical parameters and refractive index of the resonator. The numerical results based on the finite-difference time-domain method can be accurately explained by the resonant theory. Meanwhile, the transmission characteristics of the drop waveguide are influenced by the coupling distance between the resonator and drop/bus waveguides, which can be exactly analyzed by the temporal coupled-mode theory. Additionally, it is found that the drop efficiencies can be improved by a factor of more than 1.8 when a reflection feedback is introduced in the bus waveguide.