Subwavelength filter and sensor design based on end-coupled composited ring-groove resonator

Abstract

A plasmonic filter and sensor is designed based on an end-coupled ring-groove composited resonator (RGCR). According to the magnetic field distributions of the resonance modes, a horizontal or vertical groove is added to the perfect ring resonator, and the transmission peaks for the 1st and the 2nd modes can be linearly changed by the length of the groove. In this case, the proposed structure can act as an on-chip optical filter with flexible wavelength manipulation. When the groove is rotated with an angle of  λ/4, Fano resonance arises due to the mode interference. Dual asymmetric sharp transmission peaks are achieved around the wavelength of the former 2nd resonance mode. High figure of merit and high sensitivity are obtained for the structure, and it is believed that the device can find widely applications in the biochemistry sensing area. The corresponding spectra and the propagation characteristics are numerically investigated by using the finite-difference time-domain method.