Near-field Imaging Of Surface Plasmons In InAs Nanowires

Surface plasmon polaritons(SPPs)is a boson-type quasiparticle,coupling photons with free electrons on metal-dielectric interface.Due to the ability of breaking the traditional diffraction limit,the nanoscale manipulation of photons and enhanced light-matter interaction endowed by SPPs have been realized and attracted many attentions.The SPPs exist in various materials including conventional noble metals,novel low-dimensional materials and topological insulators.However,the tunability and application of SPPs in conventional metals are limited due to its strong electron-phonon interaction and large density of state.With the help of tunable concentration of charge carriers and unique electronic structures,the semiconductor materials support SPPs with high quality factor and show great potential for the future plasmonic applications.Indium arsenide(InAs),a prototype compound of ?-? family with a direct narrow band gap and high electron mobility,has becoming an attractive candidate in plasmonics.In this thesis,the optical properties of SPPs in InAs are studied based on the burgeoning near-field optical imaging method and finite boundary elements method.The thesis is divided mainly into three parts.Firstly,we realize the real-space launching and characterization of SPPs in InAs nanowires,through the localized enhancement of electric field in near-field optics.Secondly,we use the FEM(finite elements method)to simulate and analysis the experimental polaritonic images.The experimental results quantitatively agree well with the numerical simulations and the concentration of charge carriers can be extracted from the simulation.Thirdly,we found that the properties of surface plasmons,including wavelength,dispersion,confinement factor,quality factor,are influenced by the nanowire size and the supporting substrates.In summary,we report the first real-space observations of surface plasmons in one-dimensional InAs nanowires with nanoscale resolution.The observed surface plasmons exhibit low-loss,high-confinement and long propagation length.Meanwhile,we realize the tunability of SPPs in nanowires,which paves the way for light nano-manipulation and future polaritonic circuits.