Transmission characteristics of a Y-shaped MIM plasmonic waveguide with side-coupled cavities

A plasmonic Y-shaped metal-insulator-metal (MIM) plasmonic waveguide with two side-coupled Fabry–Perot (FP) resonant cavities is proposed. Simulation results show that there is a stopband existing in the transmission spectrum of each output port. When the lengths of the two cavities are equal, the transmission spectra of the two output ports are almost coincident. But if they are not equal, the two stopbands are not in the same place. Meanwhile, the transmission dip of one output port corresponds to the transmission peak of another port. By adjusting the length, width and refractive index of the two FP cavities, one can control the resonant wavelength of each cavity to further achieve functions of filtering, power splitting, switching and refractive index sensing. Results show that the sensing sensitivity is up to 1280 nm/RIU with its figure of merit above 200 when the waveguide is used as a refractive sensor. The proposed waveguide structure has potential applications in the fields of integrated optical filter, nano-optic switch, power splitter and refractive sensor in subwavelength scale.