Optimization Design, Preparation And Characterization Of Wide Angular Broadband Antireflection Coatings

The optimization design and deposition techniques of omnidirectional broadband antireflection coatings were systematically studied in this paper. The antireflection coatings based on glass slide has been designed by a computer program using the hybrid genetic algorithm. The single layer nanorod SiO2 coatings grown by oblique angle deposition using electron-beam evaporation have been obtained. With application of X-ray Diffractometer (XRD), X-ray energy dispersive spectrum (EDS), Field Emission Scanning Electron Microscope (FESEM), Atomic Force Microscope (AFM) and Spectrum Type Ellipsometer, their superficial morphology, phase structure, constitution and refractive index dispersion ware studied. On that basis the four-layer antireflection coatings with a gradient refractive index was gained, and their omnidirectional broadband anti- reflection characteristics were discussed by using Ultraviolet Visible and Infrared Spectrophotometer. The results were as follows:(1) The four-layer antireflection coating system with a gradient refractive index was gained. It plays a very good role in minus reflectivity for the visible light when the incident angle ranges from Odeg to 75deg, and the total average wide-angle visible spectral reflectivity can be reduced to 0.21% in this scope.(2) All the SiO2thin films deposited at different oblique angle had nano tilt rod structure, when the deposition angle becomes big this kinds of structure present more obvious and the tilt angle turn lager.(3) Nano tilt rod monolayer SiO2 films with different refractive index ranging from 1.46 to 1.11 were gained by changing the deposition angle. The relationship between deposition angle and refractive index has been found, moreover, the corresponding relations of one film's actual thickness and the thickness monitoring by quartz crystal were also found.(4) According to the result of the optimization and the information of refractive index obtained above, the four-layer wide-angle broadband antireflection coatings were prepared successfully.