Nonlinear Analysis of Spectral Emissivity on Evaporated Gold Layer

The relation between the thickness of the other material on the base metal surface and the spectral emissivity hasn't yet been clarified.The authors choose SUS304 as the base metal and examined as follows. Gold is evaporated on the SUS304, whose wavelength dependency of spectral emissivity in the visible region and neighboring (0.38∼0.90 μm) is totally different. As the result, the spectral emissivity changes from the value of SUS304's emissivity as the layer thickness increases from 0 μm. When the layer thickness reaches to 0.05∼0.07 μm, the emissivity gradually shows asymptotic convergence to the emissive value of the gold. Generally the spectral Emissivity depends on gold layer thickness. However, the spectral emissivity is constant (0.40) at the wavelength 0.53 μm, which is independent of the layer thickness and shows that is a fixed point. The above result (fixed point) does not comply if it is applied to optical dispassion formula of linear analysis. It means the relation of spectral emissivity between a layer thickness and a wavelength is not always linear.This study considers the spectral emissivity of evaporated gold layer, where the emissivity depends on layer thickness, is analyzed by the nonlinear dispersion model of optical interference phenomenon. The wavelength dependency can be explained by nonlinear behavior of free electron model and analyzed the data calculated from nonlinear dispersion formula, which can justify the fixed point.