Tunable band-pass plasmonic filter and wavelength triple-channel demultiplexer based on square nanodisk resonator in MIM waveguide

Abstract

This paper proposes a wavelength demultiplexer (WDM) in a metal-insulator-metal (MIM) waveguide based on square cascade resonators, which is numerically simulated using the finite difference time domain (FDTD) approach. WDM's basic construction is a plasmonic filter with two waveguides at the input and output (bass and drop) and a central cavity coupled horizontally to two square nanodisks. The proposed demultiplexer is formed by stacking three examples of these filters and square resonators with different dimensions and with a vertical cavity and a waveguide at the structure's input. The simulation results show that in the designed structure, the Full Width at Half-Maximum (FWHM) in some channels is around 10 nm. The proposed WDM has a cross talk effect of less than − 25 dB. In fact, when compared to structures at its level, this structure has a high sensitivity, a low cross talk effect, and a proper Figure of Merit (FoM). If the geometric parameters and insulation's refractive index (RI) are set appropriately, the transmission qualities are able to tune to desired level. The proposed structure has the potential to be utilised in optically integrated circuits, nanosensors, to develop into a 1 ×N demultiplexer, and ultracompact plasmonic devices.