Study On The Semi-Classical Electromagnetic Properties Of Nanostructures Based On FDTD Method

With the rapid development of science and technology, all kinds of electromagnetic properties of new materials have become the focus of people’s research. In this paper, the research of nano materials is one of the hot spots.Nanostructure is a kind of structure that is formed on the basis of the material unit which has a dimension to reach nanometer level, that is, below 100nm. The nanoscale material unit includes a variety of species, and the natural nano particles and the artificial nanometer size pore diameter are all nanostructures. Because the research of experimental technology and manufacturing technology is becoming more and more mature, the research of metal nanostructure is possible. It is well known that there are great potential applications in sensing, optics, electron optics and so on, therefore, more and more attention of researchers in all directions. However, because of the size of nano materials and experimental technology, many important issues are neglected, waiting for the further study. Usually, the classical electrodynamics explain the properties of medium structures well.In this paper, we mainly study the optical properties of some typical structures of nano materials. A large part of the optical properties of this structure are related to the system, such as the structure of the system, the composition and the media, etc. In particular, when the interaction of noble metal and light can cause the conduction band electron excitation on the nanostructured surface, a coherent oscillation, which is called the focalized surface plasmon resonance (LSPRs), is formed. The optical properties of metal nanostructures, such as LSPRs, have very big research value.However, with the study of medium size reduction, such as study of only a few nanometers structure, this structure may containing only a few atoms, there bias of experimental data and results of classical electrodynamics can not be ignored, this bias, can not be explained accurately by using classical electrodynamics research method. Even a relatively large size, the deviation will be found, but due to other reasons, this deviation is not obvious. In order to effectively study the deviation, the introduction of the a new research method is in this paper, which is studying the optical properties of metal nanoparticles and the optical properties of the deviation through the finite-difference-time-domain method (FDTD), called the optical properties of nonlocal properties.The main work of this paper are:1 Efficient fitting of experimental data of nobel metals.Modified the classical Drude+Lorentz medium electric constant expression, adding the spatial dispersion characteristics, make it related to the wavevector k. At this point, the dielectric constant is related to its neighboring structure. And then describe the electromagnetic characteristics of nobel metal accurately.2 The modified Drude+Lorentz model is added to the FDTD for discrete. The C++ program containing the modified dispersion model is obtained. Its numerical simulation is realized.3 Through the electromagnetic simulation of typical structure, the numerical results are compared with the analytical results, which verify the feasibility of the method. The extinction cross section is compared with the absorption effect in the nanometer size mainly, which occupies the main position.4 The optical properties of half classic 1D,2D and 3D nanostructures were studied, by changing the structure parameters, the 2D and 3D results cross comparison and analysis influences on the nonlocal character, obtained the general characteristics of the nonlocal properties.