Study On The Modified Lorentz-Drude Model Of Noble Metal Dielectric Parameters And Its Optimization Analysis Based On The Differential Evolution Algorithms And Film Thickness

Surface plasmon wave which is universally applied in the nanoscale optical waveguides and optical devices in the future, becomes a hot spot in the research. Due to Surface plasmon wave occur between the surface of the noble metal and medium, so the accuracy of noble metal dielectric constant has a decisive effect on the choice of materials and performance of nanoscale devices. Based on previous research, dielectric constant of noble metal arise different value following the diversification of wavelength. This makes us generate question about the results of calculation parameters in the surface plasmon waveguides. It has proposed Drude model and Lorentz_Drude model which not get precise dielectric constant at the random wavelength. By analyzing the reason that the dielectric constant occur sharp arise below 600nm, we alter the part of interband base on traditional Lorentz_Drude model to accomplish the modified Lorentz_Drude model. We use the Differential Evolution algorithms to achieve the new Lorentz_Drude model fitting with the latest experimental data of noble metal such as gold, silver, copper, besides determine interrelated parameters at Full-Band. Based on the modified Lorentz_Drude model, the calculation of plasma frequency and relaxation time are more accurate than the previous value and then effective mass of the electron is more dependable.When thickness of noble metal film diminishes at nanometric scale, generating size effect, volume effect and so on will make the dielectric constant of noble metal occur variation. In the previous research, it exists defect that F-S model and M-S model has been proposed. Totally considering the surface scattering and grain boundary scattering of the metal films, we proposed the FS-MS model which can exactly express the fluctuant conductivity of metal following the change of the noble metal film. With the help of the modified Lorentz_Drude model, we obtained noble metal film related to the dielectric constant of noble metal. For the design of surface plasmon nanoscale devices, it has been proposed that theoretically foundation which is the selection thickness and dielectric constant of noble metal.