Theoretical and experimental study on scattering reduction of single-layer TiO2/SiO2 optical films

The work aims to reduce the scattering loss of single-layer optical films. The theoretical basis of the scattering reduction of single-layer optical films was proposed according to the theory of coherent scattering. A single layer of TiO2 with optical thickness l/2 and SiO2 with optical thickness l/4 were respectively deposited on K9 glass by electron beam thermal evaporation technique. The surface roughness of the film was adjusted by changing the process, and the horos scattering instrument was used to measure the bidirectional reflection distribution function on the surface of the optical element before and after coating. For the single-layer TiO2 film with optical thickness l/2, when the ratio of the upper and lower interface roughness of the film was 0.7, the scattering reduction effect was obviously better than that with the ratio of 0.6 and 0.9, and the closer the ratio was to 0.71, the more obvious the scattering reduction effect was. For the single-layer SiO2 film with optical thickness l/4, when the ratio of the upper and lower interface roughness of the film was 0.7, the scattering reduction effect was obviously better than that with the ratio of 0.8 and 1.4, and the closer the ratio was to 0.13, and the more obvious the scattering reduction effect was. The scattering resistance of the single-layer optical film is not only related to the interface roughness of the optical film, but also closely related to the optical thickness of the film and the refractive index of the film. For single-layer TiO2 and SiO2 films with specific optical thicknesses, when the roughness ratio of the upper and lower interfaces of the film satisfies the subtraction scattering interval, the effect of subtraction scattering can be achieved, and the closer the ratio is to the optimal subtraction ratio, the better the effect of subtract scattering is. Under certain conditions, when the surface roughness of the film is greater than the surface roughness of the substrate, it is also possible to achieve the effect of reducing the scattering. © 2019, Chongqing Wujiu Periodicals Press. All rights reserved.