Tunable single-mode bandpass filter based on metal–insulator–metal plasmonic coupled U-shaped cavities

Abstract

A compact plasmonic bandpass filter based on metal-insulator-metal plasmonic waveguides and a coupled U-shaped cavity is proposed in this study. Air and silver are used as insulator and metal materials and silver is characterised by the Drude model in the simulations. By tuning the height of the designed cavity, it is found that the resonance wavelength can be easily adjusted. Furthermore, the quality factor of the designed filter can be increased by increasing the cavity numbers. One, two or three cavities can be used to generate single-mode filters. Finally, by sweeping different structural parameters, the effect of them on transmittance spectrum is investigated. All results are obtained by the finite-difference time domain method. The proposed structure due to its remarkable properties such as being a single-mode filter, having a compact size, tunablity of the resonance frequency and its variable quality factor can be used in complex integrated optical structures such as demultiplexers and so on.