Research And Preparation Of The Ultra-broadband Solar-protective Thin Film

Some of the infrared remote sensing applications,such as infrared horizon sensor,working on the earth's synchronous orbit satellites have two disadvantages:Firstly,the sensor can't completely avoid the direct incidence of solar radiation because of the design needs and its operating mechanism.Secondly,the solar radiation directly affects the properties of the infrared remote sensor because of the absorption of the radiation by the optical substrates such as Ge and Si.The severe situation is that results in the sensor blind.So a solar-protective optical system is introduced in these sensors and one of the key components is a multiplex infrared lens which is used as a window of the system.The solar-protective function is mainly realized by two kinds of different coatings,the ultra-broadband solar–protective coating and broadband antireflective?AR?coating.The ultra-broadband solar-protective coating is used to minimize the solar radiation and AR coating is to enhance the efficiency of the long wave infrared band of the system.To prepare effective solar-protective coatings,which meet the demands of the system,the optical thin film materials,the design method and the deposition technics are studied in this thesis.Both ZnS and YbF₃ thin film materials,which selected from several commonly used ultra-broadband thin film materials,are studied by a series of experiments.The properties of ZnS thin film are relatively stable,therefore only the influence on the properties of ion beam assisted deposition with different energy was analyzed in this thesis.For YbF₃ materials,the influence of deposition methods,deposition thickness,deposition temperature and the parameters of ion beam were studied.The optical constants of ZnS and YbF₃ films were obtained by fitting the transmittance spectra.These data were valuable for the coating's design.According to the results,the final preparation process was generalized as:ZnS film is deposited by resistance heating evaporation;YbF₃ film is deposited by electron beam heating evaporation;the deposition temperature is 200?;ion beam assisting was not adopted.Good design methods were used to get an effective solar-protective coating and AR coating.A software assisted automatically monitoring the thin film thickness is written,whose alarm system can reduce the preparation error of the film.According to the optimized design and deposition process,effective solar-protective coating and AR coating were prepared.The properties of the coatings satisfied the demands of the system.They can also endure the test of space environment.The ultra-broadband solar-protective coating was also proved that can be used as a kind of effective dichroic beam splitter.