The Research Of The Coupled-resonator Based On A Stub And A Nanodisk Resonator

A coupled-resonator structure consisting of a stub resonator and a nanodisk resonator is proposed and numerically investigated by using a 2-dimension finite element method.Simulations results show that two resonant modes occur in the transmission spectra and the sharp and asymmetric Fano-lines increase the wavelength resolution.We also analyze the two resonant modes properties of the structure and design a similar structure supporting only one resonant mode which has better wavelength resolution.Our models are important for improving the wavelength resolution in plasmonic devices and the sensitivity in sensors.Surface plasmon polarizations(SPPs),known as electromagnetic waves coupling to the propagating free electron near the metal-dielectric interfaces,have been considered as energy and information carriers to overcome the classical diffraction limit of light in conventional optics.By now,a large number of devices based on SPPs have been investigated and analyzed both theoretically and experimentally,such as splitters,modulators,mirrors,Bragg reflectors,sensors and all-optical switches.As an important plasmonic waveguide,the metal-insulator-metal(MIM)structure has strong confinement of light with an acceptable length for SPPs propagation.Some simple wavelength-selective MIM waveguide structures,which have great importance in modern optical communication,have been proposed and investigated,such as plasmonic tooth-shaped filters,plasmonic electro-optical switching.However,all these structures have resolution that is low for practical applications in future.In this paper a coupled resonator is proposed to improve the wavelength resolution.In conclusion,a coupled resonator structure based on a stub resonator and a nanodisk resonator is proposed and calculated by 2D-FEM.Simulations results show that two resonant modes appear in the transmission spectra.The sharp and asymmetric Fano-lines increase the wavelength resolution.We can obtain the transmission spectra we need by modulating the geometrical parameters and the refractive index n of the nanodisk.In addition,we design a similar structure supporting only one resonant mode.By extending the length of the input/output waveguide,the second resonant mode can be effectively suppressed and the wavelength resolution of the first resonant mode can be improved.The proposed structures may be applied to highly integrated optical circuits and optical switching.