Study on the Interference Effect in Plasmonic Resonator-coupled Waveguide Systems

Author:Lin Zuo

Supervisor:wang ling ling


Degree Year:2018





The phenomenon of interference is the most direct evidence of the volatility of matter.The rise of plasmonics makes it possible to regulate light at the sub-wavelength scale.Surface plasmon is a surface electromagnetic wave localized at the metal-medium interface.Its localization is a key factor to overcome the traditional optical diffraction limit,and its propagation loss is a key factor that determines the propagation distance of this surface electromagnetic wave.However,the surface plasmon mode of metal nanostructures due to non-radiative loss is so large that active control cannot be used to hinder its practical application.This dissertation aims at the characteristics of strong localization,low loss,and dynamic tunability of resonance frequency in graphene plasmonics.Using theoretical analysis,numerical simulation and combined with reported experimental results,the interference of surface plasmon waveguide mode is explored.Physical mechanisms and their potential applications in plasmon-induced transparency,induced absorption,and filter elements are discussed.On the basis of previous work,this research focuses on the theme of the interference effect of the surface plasmon waveguide mode,and expounds six items from three perspectives of constructive interference,destructive interference,and Fabry-Perot interference:A near-field-coupled graphene plasmonic-induced transparency waveguide and its coupled mode theory model are proposed;the transmission and resonance properties of the structure are studied using the finite-difference time-domain method,and the width of the graphene nanoribbon is obtained.The resonance wavelength dependence.The coupled-mode theory of surface plasmon waveguides is used to further clarify the physical image of the structure,and the results of theoretical calculations and numerical simulations are in good agreement.On this basis,the near-field interference mechanism and resonance characteristics of near-field coupled graphene plasmon-induced transparent waveguides are studied.The results show that the graphene nanoribbon resonator 1 is directly excited due to the near-field coupling effect between the graphene nanoribbon resonator 1 and the graphene plasmon slab waveguide and supports the super-radiation mode.Due to the large longitudinal coupling distance between the resonator 2 and the slab waveguide,it cannot be excited directly.It can only be excited by the near field coupling with the resonator 1and supports the sub-radiation mode.The destructive interference between super-and sub-radiation modes leads to the appearance of induced transparent peaks,and both the lateral and longitudinal coupling strengths are important factors affecting the height of the transparent peak.In addition,the dynamic window frequency can be dynamically adjusted by changing the Fermi of graphene,which is the most distinctive feature of the near-field coupled graphene plasmon-induced transparent waveguide.A phase-coupled graphene-induced plasmonic-induced transparent waveguide and its transfer matrix model are proposed;the phase-coupled metal-medium-graphene and other phases are studied in conjunction with the transfer matrix method,coupled-mode theory,and finite-difference time-domain calculations.Far-field interference mechanism induced by exciton-induced transparent waveguides.The waveguide is composed of a cascade of graphene nanoribbon resonators and a graphene slab waveguide.The formation of the transparent window is attributed to the superposition of resonances of the two detuned graphene nanoribbon resonators.The evolution of the transparent window is closely related to the optical path difference between the two graphene nanoribbon resonators accumulated on the graphene slab waveguide,and the peak value of the transmissivity shows a periodic change with the increase of the far field coupling distance.The spacing between the metal-graphene plate waveguides modulates the effective refractive index of the region,which provides a new degree of freedom for adjusting the phase difference of the plasmonic waveguide modes on the entire graphene plate waveguide.By decomposing the transmittance expression derived from the transfer matrix to obtain the corresponding intensity term and phase term,it is clear that the phase difference accumulated in the metal-medium-graphene waveguide region is the plasmon induced transparent window transmission intensity and symmetry.The key factor.This section also discusses the effect of carrier mobility on the transmission of graphene.Studies have shown that by optimizing the preparation process of the graphene material itself,defects such as defects that affect the carrier mobility are reduced,and a transparent window of high transmittance and ultra narrow band is obtained.In addition,similar to the slow light characteristics of plasmon-induced transparent metamaterials,the group delay response of near-field coupled waveguides is not uniquely determined by the coupling strength,but is also determined by the inherent loss and waveguide of the graphene nanoribbon resonators themselves.Coupling loss.The refractive index of the group of phase-coupled waveguides can reach the order of 300,which is determined by its own narrow bandwidth and high transmittance.In this section,the physical model of the phase-coupled waveguide is extended to the case of a three-resonator cavity.The results of the study once again demonstrate the accuracy of the model and can still achieve a group index of 300 when the entire waveguide length is doubled.Multi-zone slow light characteristics.A dynamically adjustable graphene-induced plasmonic-induced transparent waveguide and its coupling mode theory model are proposed.This chapter studies the graphene plasmon-induced absorption waveguide by using the coupled mode theory and the finite-difference time-domain method,respectively.The transmission and resonance characteristics.The three-level model of atomic media is used to describe the coherent optical path in the waveguide structure.By fitting the results of numerical calculations,it is demonstrated that the formation and evolution of plasmon-induced absorption windows are attributed to metallic super-radiant resonators,respectively.The constructive interference with the graphene nanoribbon sub-radiation resonator involves the coupling strength between its resonant modes.By optimizing the lateral coupling distance of the two resonant cavities,continuous adjustment of the absorption intensity can be achieved,which is attributed to the coupling distance between the antinodes of the two resonant modes that determines the near field coupling strength between the two resonant cavities.By controlling the Fermi energy of graphene,the absorption window can be shifted in the spectrum,so as to achieve active control of the induced absorption resonant frequency of plasmons.By adding graphene nanoribbons,dual plasmon-induced absorption effects can be achieved in the integrated waveguide.While ensuring high transmittance,the waveguide system can achieve a slow light response with a group delay of 1.0 ps.A bilayer Dirac plasmonic resonant cavity coupled waveguide is proposed.By analyzing the dispersion characteristics of the double Dirac semi-metal slab waveguide,the advantage of the symmetric coupling mode in terms of locality and transmission loss is clarified..The application of the waveguide mode is illustrated by designing a bandpass filter consisting of two silicon strips embedded in a double Dirac half-metal slab.The resonant frequency of the filter shows the dependence on the cavity length and silicon ribbon width between two Dirac semi-metal films.The small changes in the Fermi energy in the Dirac semimetal can make the transmission spectrum dynamically adjustable in frequency.A local enhanced Dirac half-plasmon plasmonic waveguide is proposed.By studying the dispersion relationship and propagation loss of the plasmonic waveguide structure,it is found that in a certain optimized frequency band,such surface plasmon polariton is found.With enhanced locality but reduced loss characteristics.This characteristic is not available in the traditional precious metal plasmon waveguide mode.Unlike the waveguide structure studied in the previous chapter,the Dirac half-metal-medium-metalplasmonwaveguidecanachievewide-bandmode confinement up toλ0/15,and has a relatively low loss of about 1.0 dB/λ0.In addition,terahertz waves can be efficiently transmitted through an ultra-narrow slit width less thanλ0/2000.As an application,by introducing two silicon strips,a filter function capable of dynamically adjusting the resonant frequency at a deep subwavelength can be realized.In summary,this paper starts with the dispersion characteristics of the plasmonic waveguide mode and combines three typical phenomenological theoretical models to systematically explore graphene and Dirac semi-metal and metallic plasmon waveguides.The plasmon-induced transparency,induced absorption,and Fabry-Perot resonance effects caused by the interference of modes,and the potential applications of several effects in filtering,sensing,and slow light,are discussed.They are highly integrated and active.The design of controlled plasmonic waveguide devices offers new ideas.