Excitation Of Local Field Based On Bowtie Antenna

Local field excitation is an important subject in micro and nano optics.It is generated by the collective oscillation of free electrons in the antennna under specific light polarization.It plays a critical role in super-resolution imaging,Raman fluorescence enhancement and particle manipulation for its strong light field enhancement and localization ability.This thesis closely focuses on excitation of local light field in Bowtie antenna.Based on two different physical mechanism,we realize super-resolution local light field and develop some typical applications.Combined with simulations and novel antenna fabrication methods,the light enhancement,transmission efficiency and localization ability of antenna are optimized.Direct writing lithography with high resolution is achieved based on the optimized near-field scanning optical lithography system.Local field is also excited innovatively by an electrical apparatus.Through inelastic tunnel process,energies are transferred to plasmons.This output power of electrically pumped nanosource can reach up to 1.4 nW and the efficiency is 10-4.The contents of this thesis are listed below:1.Combined with finite time domain difference method(FDTD),the relations between the geometric parameters of Bowtie antenna and light enhancement,localization ability and transmission efficiency are studied.The critical parameter is concluded.The resonance characteristic of antenna is analyzed.Combined with the transmitted spectra and waveguide theory,the effects of FP resonance and plasmonic resonance are evaluated.According to the different applications,the structure of Bowtie can be determined by these analysis.2.Aiming at the existing problem of antenna fabrication,we propose one backside milling method to achieve Bowtie antenna with gap size smaller than 9nm.Combined with the ultrasmall gap size and flexural passive compliant stage,near-field scanning optical lithography with linewidth of 16nm resolution is achieved.3.Since the localization characteristic of Bowtie antenna can only exist at the near field plane,evanescent light field exist in the propagation direction.In order to extend the working distance of Bowtie antenna,we exploited metamaterials to shape the evanescent light field.Evanescent field under different dispersion relations is analyzed.Through changing the parameters of layered metal-dielectric-metal(MIM)materials,the hyperbolic dispersion is chose.The exposure apparatus of near-field scanning optical lithography can be optimized to achieve the focus depth up to 100nm.4.The electrically pumped nanosource is based on the tunnel behavior.During the tunnel process,parts of electrons will tunnel elastically across the barrier without energy losses.The other part of them will tunnel inelastically and transfer energy to plasmons or phonons.The generation of plasmons will form local filed under the antenna.Here,we propose a novel design of Bowtie antenna.Through a well-controled electromigration process,sub-nanometer tunnel gap is formed and located accurately at center of Bowtie antenna.Through Simmons model,the IV curve of tunnel process can be fitted to deduce the tunnel gap of 0.6nm.The spectra of electrofluorescence are measured and the multiple resonace peaks are observed.Fitted by Lorentz functions,the multiple peaks can be explained by resonances of different orders of localized surface plasmons modes.Also,by changing the geometric parameters,the energies of LSP modes can be tuned from 1.39eV to 1.9eV.The output power of electrofluorescence is measured to be 1.4nW,which is two orders higher than previous reports.This is also the highest one in the radiation of single plasmonic antenna.This mainly attributes to three factors,the high tunnel current(micro ampere),the multiple spontaneous decay channels brought from multiple LSPs modes and the optimized radiation efficiency of antenna.Innovations of this thesis are listed below:1.Based on backside milling method,we fabricate the Bowtie antenna with ultra small gap.Combined with flexure compliant stage,near-field scanning optical lithography with linewidth of 16nm resolution is achieved2.We propse the idea to excite the local light field by an electrical method.Inelastic tunneling mechanism is analyzed.A new plasma antenna is designed to reduce the loss of plasmons in the tunneling junction and to improve the output power of electroluminescence.3.Based on a well-controlled electromigration process,sub-nanometer tunnel gap is formed,which is helpful to increase the tunnel current and output power.4.We analyze the spectra characteristic of electroluminescence,and conclude the multiple peaks originates that the resonance of different orders of LSPs modes.