Effect Of Atomistic Protrusion At Nobel Metal Surface On The Spontaneous Emission Enhancement

Surface plasmon is an electromagnetic mode formed by the interaction of free electrons and electromagnetic field on the metal.The electromagnetic field can be bound to the nanometer scale near the metal surface,which provides an important means for manipulating and controlling light waves at the nanometer scale.The local field enhancement effect of surface plasmons has been widely used in many fields,including spontaneous emission enhancement,novel integrated optoelectronic devices,highly sensitive biological detection,and novel light sources.Various resonant and non-resonant metal nanostructures are widely used to enhance the local field.The introduction of atomic scale protrusion on metal surface and the use of “lightning rod effect” has become a research frontier.This dissertation mainly studies the spontaneous emission properties of atoms protrusion on the precious metal surface and their relevant theoretical methods.The main details are as follows:In Chapter 1,we mainly introduce the theory and numerical simulation method of spontaneous emission of atoms in surface plasmon nanostructures,including the metal local light response model(LRA),the nonlocal hydrodynamic model(HDM),the generalized nonlocal optical response model(GNOR)and the quantum hydrodynamic model(QHT).The full wave simulation method of Photon dyadic Green function and quasinormal mode are emphasised.In Chapter 2,four optical response models are adopted to investigate the spontaneous emission enhancement around a gold atomistic protrusion with a cone or a truncated cone shape of different sizes,including the LRA,the HDM,the GNOR and the QHT.Compared with LRA,the spontaneous emission enhancement blueshift and decrease rapidly under the HDM model and GNOR model.However,the spontaneous emission enhancement redshift and have little effect on the peak under the QHT model.The higher the protrusion is,the larger enhancement can be observed.The spontaneous emission enhancement of a truncated cone shape structure is stronger than a cone shape structure.In QHT,the spontaneous emission enhancement increased with the decreasing of the truncated cone radius.But the peak decreases under the HDM model and GNOR model.In Chapter 3,the spontaneous emission properties of atoms at the center of the gap for nanosphere dimer size,gap size,protrusion size etc are calculated when the optical response for metal is under the LRA,HDM and GNOR.The results show that the dimer gap thickness has a great influence on the enhancement of spontaneous emission,and the smaller the gap distance,the more obvious the enhancement effect.When the gap distance is small,the protrusion can effectively increase the spontaneous emission of atoms.Compared with non-protrusion structure,the enlargement factor is 20 times in the double protrusion structure.However,the enlargement factor is about 5 times under the nonlocal response of HDM and GNOR.When the gap distance is larger(3 nm),the enhancement effect caused by the protrusion structure is not obvious.In Chapter 4,the spontaneous emission of atoms in micro-nano structure can be expressed by photon dyadic Green function.It is of great significance to quickly and accurately calculate the photon dyadic Green function in metal nanostructures.In this chapter,a set of quasinormal mode numerical simulation platform in metal nanostructures is developed.This method can quickly obtain the photon dyadic Green function at different positions and jump frequencies.Under the local and nonlocal optical response model,the results show that the spontaneous emission spectrum is consistent with the full-wave simulation results for sphere,double sphere dimer and protrusion dimer structure.When the quantum emitter are equidistant from the metal surface,the spontaneous emission at the lower order mode of the dimer is greater than the situation of sphere.In Chapter 5,nanoscale precious metals not only have quantum scale effects such as nonlocal,spill-out and interface scattering but also have interband transitions and shielding effects in their shell electrons.In this chapter,we developed a set of quantum hydrodynamic simulation methods for surface plasmons in noble metal nanostructures.Taking the experimental data and TD-DFT results as reference,the influence of the ion-free polarization thickness of the interface on the ground state charge density and resonance frequency was systematically studied.The influence of the local environment at the metal-dielectric interface on the surface plasmon resonance was studied.A quantum hydrodynamic simulation method for accurately simulating the relevant parameters for the surface plasmon resonance frequency of precious metal nanoparticles was obtained.In Chapter 6,makes a brief summary and outlook.