Narrow-Band Plasmonic Filter Based on Graphene Waveguide with Asymmetrical Structure

A narrow-band plasmonic filter based on graphene waveguide with asymmetrical structure is proposed, and the corresponding transmission characteristics are investigated. The asymmetrical structure consists of two sets of five air trenches with different trench sizes. Since the Bragg wavelength could be changed with the length and depth of each air trench, the bandgap (or the passband) of the single set with five short thick air trenches and the passband (or the bandgap) of the single set with five long thin air trenches are overlapped and the cascaded transmission of the two structures is very low in a certain wavelength range. By using the finite-difference time-domain (FDTD) method, a narrow-band transmission peak with 3-dB bandwidth of 0.12 mu m could be obtained in the mid-infrared region around 6.9 mu m.