Fano Resonances Based On Surface Plason Polartitions And Their Applications In Information Field

Fano resonance has emerged as an important area in the field of plasmonics over the recent past,because surface plasmon polaritons(SPPs)can overcome the diffraction limit and confine light in deep sub-wavelength dimensions.Due to the advantage for enhanced bio-chemical sensing,spectroscopy,and multicolor nonlinear processes,the multiple Fano resonances become more important and have gained much attention.Among all the nanostructures,the metal-insulatior-metal(MIM)waveguide structures have attracted many researchers attention because these structures exhibiting more suitable for the highly integrated optical circuits due to their deep-sub-wavelength confinement of light.And based on the MIM waveguides,a large number of devices,such as splitters,sensors,optical switches,nonlinear and slow-light devices.Thus,investigations of the response line-shapes and the physical mechanism in the coupledresonator systems are of importance for designing complex functional plasmonic devices as well as for improving their performances.The main research contents and innovations of this paper are as follows:1.Starting from the classical Maxwell equations,the basic principle of surface plasmon in a single interface and multi-layer metal/dielectric interface is discussed.Subsequently,two important theoretical models commonly used in this thesis are studied:scattering matrix theory(SMT)and coupled-mode theory(CMT).The relationship between matrix elements in scattering matrix is introduced in detail,and the scattering matrix of partial transmission system is given.The coupled-mode theory of single-exit and two-exit waveguide-resonator systems is also discussed,and the coupled-mode formulas of the through-coupled and side-coupled systems are provided.2.The reasons for the Fano resonance in single-sided and double-sided plasmonic waveguide filters are studied from both theoretical and simulation aspects.Based on the Fano nonlinear asymmetry,a variety of plasmonic band-stop filters based on tooth structure are designed,which including single-tooth,double-tooth and three-tooth structure,as well as unilateral structure and bilateral symmetrical structure.By analyzing the system from shallow to deep,a narrow band-stop filter and a wide band-stop filter with adjustable band gap are obtained.By comparing the transmissivity curves of unilateral three-tooth and bilateral symmetric three-tooth filters,it can be found that the band-stop width of the Fano line-based unilateral three-tooth filter is much smaller than the band-stop width of the bilateral three-tooth filter when the center wavelength is basically the same.3.We reported an asymmetric plasmonic structure composed of two MIM waveguides and two rectangular cavities.And the multimode interference coupled mode theory(MICMT)including coupling phases is proposed based on single mode coupled mode theory.The MICMT is used for describing and explaining the origin of the multiple Fano resonances in coupled plasmonic resonator systems.Our proposed structure can support triple Fano resonances originating from three different mechanisms.By tuning the positions of the three Fano resonances,the transmission spectra can be well tailored and the narrow'M' type of double Lorentzian-like line-shape transmission windows can be constructed.This multiple Fano resonances can find widely applications in switches,bio-chemical sensors,slow-light devices and modulator of high density nano-photonic integrated circuits devices with excellent performance.4.We studied the transmission response of circular cavity and waveguide through-coupling system theoretically and numerically.And,three kinds of Fano resonances appeared in the transmission spectrum of the double circular cavities and the waveguide through-coupling system.Utilizing the method of decomposing the field in the waveguide,the MICMT and degenerate interference coupled mode theory(DICMT)are presented to explain the three kinds of Fano resonances.The three kinds of Fano resonances can be tuned by changing the parameters of the two plasmonic resonators,so that the coupling coefficients and coupling phases between waveguides and different resonant modes can be changed,and then the transmission response of the plasmonic system can be controlled.This small footprint together with the tunable spectral response can actualize active devices for fundamental study and applications in sensors,splitters,lasing and slow-light devices.5.We investigated the transmission response of a hybrid system composed of a VG plasmonic resonator coupled to a nanowire embedded with two-level quantum emitters(QEs).Femtosecond pulses with THz repetition frequency can be obtained by the coupling between the QEs and the plasmonic resonator in the case of continuous wave input.The repetition frequency and extinction ratio of the pulses can be freely controlled by the incident light intensity and QE number density,and the pulse widths can also be modulated below 100 fs.This provides a method for generating narrow pulsed lasers with ultrahigh repetition frequency in plasmonic resonator system,which has potential applications for generating optical clock signals at the nanoscale.