Propagation Properties And Application Of Light Wave In Metal - Based Thin Films

Because of the unique physical properties and important application, the meatl-based film has attracted wide attention and the related study becomes a very popular research field in optoelectronics. The metamaterial containing metal component has many marvelous properties and potential application value which differ from the conventional medium. In order to understand the role of metal and the physical origin of the negative refraction in artificial metamaterial, study the refraction phenomenon in metal interface has great significance. In addition, with the development of the green energy technology, metal-based thin films have been used in solar energy utilization and development areas. The solar spectrum selectivity film with high absorptance and low thermal emittance is one of the key elements in solar concentrators and solar thermal conversion systems. Special attention has been paid to the new materials with high performance and low cost, which could be used in middle and high temperatures. The study of advanced metal-based selective film can promote the development of the solar film industry.This research work focused on the light propagation characteristics of optical thin film and related applications was carried out under the above background. The dissertation mainly includes the following contents.1. We have fabricated a series of noble metal and transition metal wedge-shaped thin film with precisely controlled wedge angles by RF magnetron sputtering. In the experiment, we quantitatively measured the refraction of the light passing through the metal/air interface, and got the relationship among the apparent refraction index, incidence angle and refraction angle. The spectroscopic ellipsometer was used to measure the complex dielectric function and refraction index. The results have shown that the noble metals in the visible band have negative refraction, with the incident energy increase, the refractive angle will change from negative to positive. But the regulation is not available for transition metals in the same region.2. In terms of the result which shows the refractive angles changing from negative to positive at different wavelengths and at the noble metal/air interface, we studied and discussed those possible mechanisms of many controversial view points used to explain the physical origin of the negative refraction effect in past years, such as the plasmon resonance effect, negative permeability effect, Goos-Hanchen effect, optical magnetron effect, and so on. On the basis of the detailed calculation and analysis, we believe that the singular light refraction in the visible band relates to the group velocity and group index change caused by the dispersion characters of metal in Drude band, but not with others.3. We have designed a multi-layer interference film structure. The metal/dielectric structure consists of highly reflection metal layer, transparent dielectric layer, absorbing metal layer and surface dielectric anti-reflection layer. The high absorption was due to the intrinsic absorption of metal and destructive interference. Numerical calculations based on the rigorous transfer matrix theory have been performed for simulating the spectral properties of multilayer film stacks with different materials. The results indicate that the film structure has a good spectral selectivity suited for solar thermal applications. In experiment, we fabricated the SiO2/Cr/SiO2/Al multilayer film using the magnetron sputtering system and measured the optical property by spectroscopic ellipsometer and spectrophotometer. The experimental results agreed well with those from simulation and show a good spectral selectivity in the whole solar spectrum. The absorption can reach95% in the visible and infrared band while the total absorptance is92%. After annealing at600℃in vacuum for6hours, the film optical performance does not change, which means that the film structure has a good thermal stability. The calculation results show that the film has a low thermal emittance in high temperature. For example, in600K and1000K, the emittances of film are only0.057and0.129respectively. The metal-based absorbing film has many advantages, such as excellent nature, simple structure, wide selection of materials, simple preparation, low cost, stable performance and pollution-free production process. It is very suitable for promotion and utilization in middle and high temperature solar thermal systems.