A triangular shaped channel MIM waveguide filter

A compact plasmonic branch-shaped metal–insulator–metal (MIM) waveguide with a triangular-annular channel is proposed and investigated. The results show that all-band waves can transmit through the structure when it has transmission symmetry. As the symmetry is broken, a typical filtering function is obtained and the transmissivity of the resonance frequency depends on the destroyed degree of symmetry, which results from interference between the two branched surface plasmon polaritons waves (SPPs) propagating along the branch-shaped waveguide. Moreover, the filtering wavelength can be selected by changing the length of the triangular-annular channel. These asymmetric waveguide structures may open up new avenues toward the control of SPPs and the development of filters based on plasmonic designs.