Study On Scattering Characteristics Of Optical Thin Films By Adjusting The Optical Film Interface Electric Field Intensity And Interface Roughness

Optical film scattering is one of the key factors affecting the application of high precision optical system.It is of great significance to fabricate optical thin film components with very low scattering loss by carrying out research on the surface scattering characteristics of optical films and analyzing the factors affecting the surface scattering of optical films.In this paper,the methods of controlling surface roughness scattering and particle scattering of optical thin films are studied.Theoretical analysis and experimental research are carried out.The main content is as follows.1.Based on vector scattering theory,the scattering characteristics of spherical particles on optical surface are studied.First,the electric field intensity of the center of spherical pollutant particles on the optical surface is calculated.The electric field intensity distribution of spherical particle center on the surface of optical film with different refractive index and thickness is analyzed,and the film thickness corresponding to the minimum value of electric field intensity is taken as the optimal film thickness of optical element surface.Secondly,the bidirectional reflection distribution function and total scattering loss of the optimized thin film surface and bare substrate surface are compared.Finally,mask plate technology is used to deposit monolayer films of optimized thickness on the surface of K9 glass substrate,while the other half of the substrate does not deposit films.The bidirectional reflection distribution functions of the coated and uncoated surfaces were measured after the samples were placed in the thousand class super clean room for 48 hours.The results show that the scattering of particulate pollutants on optical surface can be reduced by optimizing the design of optical film.2.Based on the vector scattering theory of optical film,the scattering characteristics of multilayer dielectric optical films with certain interfacial roughness and the relationship between the distribution of interfacial electric field intensity are studied under the condition of satisfying the basic spectral reflectance requirements.Firstly,the electric field intensity at the interface between the quarter films?:G/(HL)~8/A and?:G/(HL)~8H/A was calculated.The calculated results show that the electric field intensity at the interface of film system?is larger,while the electric field intensity at the interface of film system?is smaller.The electric field intensity of the outermost layer interface was optimized on the basis of the film system?,and the optimized membrane system?:G/(HL)~6H0.4L1.6H1.5L0.5H/A was obtained.Then,the bidirectional reflection distribution function and total scattering loss of the three film systems are analyzed.The theoretical and experimental results show that the surface roughness scattering can be reduced by adjusting the electric field intensity of interface of the multilayer dielectric high reflection thin film.3.The surface scattering characteristics of monolayer SiO₂ and TiO₂ films with?/4 and?/2 optical thickness under the completely uncorrelated model and completely correlated model are theoretically analyzed.The effects of refractive index and thickness on the surface scattering of optical films are studied experimentally.The scattering characteristics of an 11-layer dielectric film:G/(HL)~5H/A with the central wavelength of 632.8nm are theoretically analyzed under two kinds of thin film interface correlation model.Eleven layers of dielectric highly reflective films were prepared by electron beam thermal evaporation.The thin film interface roughness and bidirectional reflection distribution function were measured.The test results show that the interface relationship of the 11-layer high-reflection thin film is in good agreement with the completely unrelated model of the film interface.