Optical Properties And Device Functions Of Gold/Silver Nanoplate Based Micro-nano Srtuctures

Localized surface plasmon resonances(LSPR)are surface electromagnetic modes that arising from the interaction of incident light with the free electrons on the surfaces of subwavelength metal nanoparticles.Since LSPR confines most energy of incident light around a metal nanoparticle,in an enhanced local field,they have promising applications in bio-sensing,chemical sensing,super-resolution imaging,and nonlinear optics,among other.Due to the structural anisotropy,relative to the isotropic nanoparticle,nanoprisms possess the tunable LSPR effect and the more significant local field enhancement effect.For these reasons,researches on nanoprisms have became more important in nanophotonics particularly in nanoparticle applications.Moreover,the LSPR intercoupling between multiple nanoparticles generate more significant local field enhancement and novel optical properties,which have important applications in near field optical imaging,nonlinear optics,surface enhanced fluorescence spectroscopy,and surface enhanced Raman spectroscopy.This thesis mainly studied the production of silver(Ag)nanoprism dimer with various geometry configurations,the hybrid optical properties and device functions based on the nanoprism dimer with various geometry configurations,nanoprism metamaterial based plasmon induced transparency(PIT)and slow-light effect.A novel and miniature Boolean logic gate was also proposed.The nanoprism has been synthesized through seeded growth method.Various Ag nanoprism dimers with different configurations were prepared by self-assembly method.The Ag nanoprisms in the prepared dimers possessed the misalignment,truncation and filleting effects.The prepared Ag nanoplate dimers with face-to-face configuration were modeled through finite element method(FEM),numerical simulation results showed that the resonant wavelengths of the extinction peaks of the dimers had misalignment dependent anti-crossing effect.The anti-crossing effect weakened as the distance between two nanoprisms increaseed.Furthermore,the extinction peaks of the face-to-face dimers composed of nanoplates with different shapes always possessed a misalignment dependent anti-crossing effect.In addition,Ag nanoprism edge-to-edge dimer was produced by self-assembly method,and modeled by FEM.The misalignment dependent switching effects of the edge-to-edge dimers were numerically studied.The dimer was normally illuminated with a linearly polarized incident light.Results showed that the intensity ratio of two extinction peaks caused by intercoupling of the LSPR between two nanoprisms in dimer could be switched by controlling the misalign length.The working wavelengths of the nano-switch could be flexibly modulated through changing the truncated length of Ag nanoprism.Silimarly,in heterodimers composed of Au and Ag filleted nanoprisms,the LSPR intercoupling between two nanoprisms also generated two extinction peaks.The intensity ratio of two extinction peaks for Ag nanoprism reversed as the tips of Ag nanoprism were filleted,whereas,the intensity ratio two extinction peaks for Au nanoprism did not reverse.For this reason,the Ag-Au nanoprism heterodimer could be used for colorimetric sensing.The performance of the colorimetric sensing could further be optimized by changing other structural parameters of heterodimer.Finally,a metamaterial based on symmetrically arranged Ag nanoprism tetramer was proposed and its PIT effect was investigated.This was also normally illuminated using polarized incident lights.Results showed that this metamaterial had a polarization independent PITeffect due to the rotational symmetry of the unit.The PIT effect and the corresponding slow-light effect of this metamaterial could be flexibly modulated by carefully manipulating the fillet radius,edge length,and thickness of Ag nanoprism.The maximum attainable group index could be up to 225.Asymmetrically arranged Ag nanoprism metamaterial was also studied and possessed polarization dependent PIT effect.Furthermore,based on the polarization dependent transmission,a novel Boolean logic gate was proposed.Simulation results showed that metamaterials with different periodicities had varying degrees of polarization dependent transmission.In addition,the resonant wavelength of the PIT effect of this metamaterial could be flexibly modulated by controlling the degree of filleted tips of Ag nanoprism.