Ultrawide bandstop filter with high sensitivity using semi-circular-like resonators

Abstract

This paper proposes a plasmonic ultrawide bandstop filter using a metal-insulator-metal waveguide cooperating with five symmetrical semi-circular-like resonators, including the silver nanorods (AgNDs). We calculated transmittance spectrum and electromagnetic field distribution employing the finite element method. The advantages of the design reveal the surface, cavity, and gap plasmon resonance effects that can simultaneously exist in the proposed device. Our design can achieve a tunable wide-bandgap by adding the AgNDs in resonators and attain an extensive stop wavelength range of 2104 nm, which is the highest bandgap width to our knowledge. Simulations results show that the AgNDs and coupling distance are pivotal factors influencing the bandgap formation, changing the resonators' resonance condition and effective refractive index. Besides, the designed filter can also serve as a nanosensor with an ultrahigh sensitivity of 7980 nm/RIU. Thus, the designed plasmonic filter can be a promising alternative candidate for optical trapping and tunable devices working in visible, near-infrared, and mid-infrared spectra.