A compact and high-efficiency dichroic plasmonic splitter based on asymmetric T-shape waveguide

•We model a compact and high-efficiency bidirectional optical splitter based on the metal–insulator–metal waveguide structure.•Due to the resonance effects in the asymmetric branches, different deserved transmission wavelengths are achieved at two output waveguides.•High transmission at the specified wavelength is achieved for the matched output port and high isolation is achieved for the other port.

An asymmetric T-shape metal–insulator–metal (MIM) waveguide is proposed to act as an efficient dichroic surface-plasmon-polariton (SPP) splitter, which consists of two drop waveguides that serve as the output ports. Due to the resonance effects in the branches, a bright mode and a dark mode at the desired wavelength are available at two ends of the branches. Therefore, high transmission is achieved for the matched output port while high isolation at the same wavelength is simultaneously achieved for another waveguide. The transmission wavelengths for two output ports are immune to each other, and only determined by the corresponding branches, respectively. This character may offer great flexibility to design the device so that one can obtain the desired transmission wavelength at one port without affecting the performance of another port. The finite-difference time-domain method is used to investigate the performance of the structure.