Wavelength demultiplexing structure based on a plasmonic metal–insulator–metal waveguide

A plasmonic multi-channel filter with individual export for each transmission peak is proposed on the basis of a metal–insulator–metal (MIM) structure. There are a series of slot cavities arrayed on both sides of the MIM slit. Surface plasmon polaritons (SPPs) are captured into the cavities resulting in multiple resonance modes. By choosing the proper positions for the drop waveguides, the first and the second resonance wavelengths can be coupled out from the corresponding exports, respectively. The central transmission-peak wavelengths can be modified by the variation of the length of the slot cavities. For a single export, there is only one peak in a large wavelength range. Two-, four-, and eight-channel filters have been designed and numerically demonstrated by the 2D finite difference time-domain method. This proposed scheme can be used in wavelength demultiplexing and fluorescence spectroscopy areas.