Research on transmission characteristics of aperture-coupled square-ring resonator based filter

In this study, a nanometric surface plasmon polariton (SPP) filter based on an aperture-coupled square-ring resonator is presented and the transmission characteristics of the SPP filter are analyzed in detail by using the finite difference time domain (FDTD) method. Results show that lifting of degeneracy exists in both even-modes and odd-modes for the regular side-coupled square-ring resonator. By introducing the aperture between the ring and bus waveguide, semi-integer resonance modes with high drop efficiency emerge in the optical transmission spectrum. Further simulation results show that semi-integer modes can be efficiently modified and linearly tuned by adjusting the parameters of the resonators such as side length of the ring, the width of the aperture and the medium inside the aperture. The simple band-stop SPP filter is very promising for high-density SPP waveguide integrations.