一个适用于数值计算的金属色散模型分析研究

A metallic dispersion model for numerical simulation

金属色散模型对数值模拟金属光学特性起至关重要的作用。本文简单分析常见色散模型与复杂色散模型之间的关系,并利用MATLAB非线性拟合方法对Au、Ag常见的色散模型进行了分析,给出在180～2 000nm波段内拟合结果。结果表明,Debye模型不适用于金属材料,Lorentz模型适合描述长波段金属介电特性,Drude模型在600～2 000nm可以描述金属介电特性,而简单明确的Drude-Lorentz模型在180～2 000nm波段能很好的拟合金属介电特性。所得结果利用Mie散射理论得到验证。

The dispersion model for metallic dielectric properties plays a crucial role in the numerical sim- ulation of metallic optical properties and dictates the result of the simulation. To date, a variety of disper- sion models have been proposed and implemented in different fields. In this paper, in order to study the suitability of the metallic dispersion models in the simulation of the optical properties Of metal surface plasmons, we show a concise analysis on the relationship between common dispersion models and com- plex dispersion models. We analyze the common dispersion models for gold and silver using the MAT- LAB nonlinear fitting method, and obtain the fitting results in the 180--2 000 nm band. The results show that the Debye model is not suitable for metal materials, the Lorentz model is suitable for describing the dielectric properties of metals in L-band,the Drude model can describe the metallic dielectric properties in the 600--2 000 nm band and the simple Drudy-Lorentz model gives a good fitting for the metallic die- lectric properties in the 180--2 000 nm band. The results are also verified by the Mie scattering theory. This paper shows that the Drude-Lorentz model is suitable for the simulation of optical properties of metal surface plasmons over a broad band of 180--2 000 nm,and it may be employed in the finite ele- ment method （FEM）,finite difference time domain （FDTD） and discrete dipole approximation （DDA） methods to characterize the metal surface plasmons.