Study On Resonance Coupling Between Surface Plasmon-polarition And Local Optical Mode In Waveguide And Microcavity

Surface plasmon polaritions(SPPs)which exhibit subwavelength localization and near-field enhancement properties are widely used in micro-and nano-sized optical components.In the nano-optical devices based on SPPs,coupling interaction between SPPs and other intrinsic resonance modes occurs,resulting in rich physical phenomena such as Fano resonance and plasmon-induced transparency(PIT).These resonant couplings realize modulation of optical properties of micro-nano structures and greatly improve sensing and detection performance of optical devices.In this dissertation,physical laws and resonance coupling properties on interaction between surface plasmon and local optical modes(optical waveguide modes and cavity-mode)are investigated respectively.The local optical waveguide resonance based on plasmon coupling can generate a Fano resonance mode with a very sharp half-peak width,which greatly enhances the refractive index detection sensitivity of device;In addition,Infrared quantum well detector based on plasmonic microcavity is proposed in our work.The resonant match between photonic state of cavity mode and electronic state of quantum well improves photon absorption efficiency in the active region of microcavity,thereby improving the detection performance.This dissertation focuses on these two kinds of local resonance based on SPP,respectively,and the main results are as follows:1.In order to reduce high loss of SPP and maintain its spatial confinement,resonant coupling mechanism and interaction characteristics between SPP(long-range and short-range SPP)and single-mode waveguides are systematically studied.The critical coupling waveguide thicknesses under different metal thicknesses and different coupling strength are calculated,and a complete phase diagram is drawn.Firstly,it is found that when SPP is coupled to WG,the system is in the PIT mode under the critical coupling waveguide thickness and the electric field is uniformly distributed in metal and WG regions.The loss and confinement can achieve a good balance under PIT condition.Secondly,the LRSPP-coupled WG is studied.A hybrid superposition of Lorentzian linear modes exists,as observed from calculating optical spectra,which shows a strongly coupled hybrid mode.Comparing with SPP-coupled WG structure,hybrid mode in LRSPP-coupled WG can achieve the best balance between low loss and wave confinement.Lastly,due to the wide resonance characteristics of SRSPP,electric field concentrates in the metal region when coupling WG.In addition,coupling characteristics between SPP/SRSPP and various order WG modes in multi-mode waveguide are studied,and it is found that with the decrease of the coupling distance,interaction evolves from weakly Fano resonance to strong hybrid coupling.While,SRSPP will simultaneously generate Fano resonance with each order WG mode.2.Aiming at the problem that harmonic oscillator model is not easy to build,a circuit model of capacitively coupled parallel RLC loop is proposed to analyze the resonance coupling mechanism between SPP and localized state modes.It is found that optical Fano lineshape and electromagnetically induced transparence can be fitted with appropriate fitting parameters.LC loop coupling coefficient and circuit dissipation coefficient can be obtained by extracting fitting parameters.Based on this,we can distinguish the condition between weak Fano resonance and strong Rabi resonance.Furthermore,plasmonic-induced transparency phenomenon is analyzed from the view of circuit phase,and it is found that the PIT in the circuit originates a transform from a single parallel LC resonance to the whole series LC resonance.We make an analogy with the corresponding phenomenon in the plasmonic optical structure.We further extend the equivalent circuit model to the coupling between short-range surface plasmons and multiple mode waveguides.3.Due to high ohmic losses for metals in metal/insulator/metal(MIM)microcavity structures,it is proposed to replace the top metal grating and bottom metal electrode layer with graphene material.The reflection spectrum under this microcavity structure is calculated by FDTD method.The influence and mechanism of graphene physical and microcavity structure parameters on photonic state of cavity mode are studied in detail.Under the optimized structural parameters,we can tune optical resonance state of microcavity to match quantum electronic transition state.Due to the high tunability of graphene material parameters,it is found that the quantum absorption efficiency of graphene-based devices is nearly 1.5 times higher than that of traditional MIM structure.