Study On Plasmon Hybridization And Optical Absorption Properties Of Metallic Nanostructures

Surface Plasmons(SPs) are the coherent delocalized electron oscillations that exist at the interface between metal and dielectric medium. Due to the evanescent nature of SPs, light field with localized enhancement is confined at a scale beyond the diffraction limit. These make SPs widely use in perfect absorbers, nanolithography, surper resolution and plasmonic nanolens. Due to the excitation of SPs, there are many unique electromagnetic properties in metallic nanostructures. Investigating the plasmonic properties of metallic structures is very important for designing high performance photonic devices. In this thesis, we focus on the plasmon hybridization, surface plasmons based-perfect absorber, and surface plasmons nanolithography. The main contents and results of the thesis are listed as bellow:(1) In the research field of plasmon hybridization, the plasmon hybridization schemes of coupled split-ring resonators(SRRs) have been studied by combining electron energy loss spectrum(EELS) and energy filter transmission electron microscopy(EFTEM). In order to investigate the plasmonic modes of the isolated SRR, and three different orientations coupled SRRs, Comsol Multiphysics and discrete dipole approximation(DDA) have been used for simulations. In order to proof the simulation results, e-beam lithography has been used to fabricate samples and EFTEM images have been obtained by experiments. By comparing the electron energy loss spectra of the isolated SRR with those of the coupled SRRs, the plasmonic mode of isolated SRR splits into two new modes in the coupled SRRs. This could attribute to the hybridization of the plasmonic modes. Besides, the coupling effects between electric dipole moments dominate the plasmon hybridization in the coupled SRRs.(2) In the research field of surface plasmons based-perfect absorber, a two-dimensional pyramid metamaterial absorber has been proposed. FDTD Solutions has been used to calculate the absorption spectra, the electromagnetic distributions, and to analyze the absorption mechanism. Due to the excitation of SPs, the slow light and the graded-index effects, the proposed metamaterial absorber could obtain near 100% absorption which covers the whole solar spectrum(0.2~2.5μm). By changing the structure parameters, the proposed metamaterial absorber could also obtain near 100% absorption in the infrared range(1~14μm). Besides, a plasmonic hybrid resonator based-infrared absorber has been proposed and analyzed for achieving high absorptivity. Due the plasmonic resonance and the Fabry-Perot(FP) resonance, the proposed absorber could obtain high absorptivity in the infrared range(8~12μm).(3) In the research field of surface plasmons nanolithography. A hemisphereical prism coupling configuration is proposed to excite SPs for the sake of holographic nanolithography. With this method, high resolution patterns could be achieved without using any masks. By adjusting the spatial and the relative phase distributions of the incident light properly, two-dimensional Bravais lattices and other periodic pattens with high resolution could be achieved.