Dual-Function Metal–Insulator–Metal Plasmonic Optical Filter

We suggest a dual-function plasmonic optical filter based on a metal-insulator- metal waveguide that has a deep subwavelength air gap 10 nm in thickness and a waveguide width of 350 nm. Because the dispersion curves of even and odd waveguide modes have different dependences on the waveguide width, and only the odd mode has a cutoff frequency, the proposed structure can have dual functionality, acting as a resonant tunneling filter for odd modes and a simple waveguide for even modes.