双源共蒸技术制备MgF_2/ZnS复合薄膜的特性

Properties of MgF_2/ZnS Composite Films Prepared by Dual-source Co-evaporation Technology

目的以MgF_2和ZnS为单组分制备MgF_2/ZnS复合薄膜,研究复合薄膜的光学性能,以获取任意折射率薄膜材料,并优化高损伤阈值激光薄膜的制备工艺。方法基于光电极值膜厚监控原理,采用电子束热蒸发和电阻热蒸发技术制备了复合薄膜,测量了复合薄膜的折射率、消光系数和透射率光谱,并对其激光损伤特性进行了研究。结果在所研究的工艺参数范围内,当Mg F_2和ZnS的沉积速率比为5∶1、4∶1、2∶1、1∶1和0.5∶1时,所制备复合薄膜的折射率分别为1.4227、1.4932、1.6318、1.9044和2.0762(波长550 nm)。复合薄膜的折射率符合正常色散,当沉积速率选取合适,可以获得介于两种组分薄膜材料之间的任意折射率。对激光损伤性能测试的结果显示,不同沉积速率比率下制备的复合薄膜的激光损伤阈值可能介于两种单组分薄膜之间,也可能高于每种单组分薄膜的激光损伤阈值,其激光损伤阈值最高比单组分MgF_2薄膜高28.6%,比单组分ZnS薄膜高96.4%。结论采用光电极值法监控膜厚,可根据不同蒸发源的蒸发特性,获得介于单组分膜料折射率之间的任意折射率材料,双源共蒸技术获取中间折射率是可行的。采用双源共蒸技术制备的复合薄膜,可改善单组分膜层的缺陷,获得高于单组分薄膜激光损伤阈值的材料。

The work aims to prepare MgF2/ZnS composite films by MgF2 and ZnS single-component materials and study the properties of the composite films in order to obtain films with arbitrary refractive index and to optimize the preparation method of films with high laser-induced damage threshold.Based on film thickness monitoring principle by optoelectronic extremum method,composite films were prepared by thermal evaporation of electron beam and resistance.The refractive index,extinction coefficient and transmittance spectrum of the composite films were investigated,and the laser damage characteristics were studied.Within the range of experiment parameters,when the deposition rate ratio of MgF2/ZnS was 5∶1,4∶1,2∶1,1∶1 and 0.5∶1,the refractive index of the composite films was 1.4227,1.4932,1.6318,1.9044 and 1.9044(at the wavelength of 550 nm)respectively.The refractive index of the composite film accorded with the normal dispersion.When the deposition rate was selected reasonably,the material with arbitrary refractive index between two composite components could be obtained.The results of laser damage test showed that the laser damage threshold of the composite films prepared at different deposition rates might be between that of two kinds of single component films,or higher than that of any single component film.The maximum laser-induced damage threshold was 28.6%higher than that of MgF2 single-component films,and 96.4%higher than that of ZnS single-component.It is available to obtain the materials with arbitrary refractive index between the refractive index of one-component film materials based on the evaporation characteristics of different evaporation sources with the film thickness monitoring by optoelectronic extreme value method.It is feasible to obtain intermediate refractive index by dual-source co-evaporation technique.The shortage of single component film can be improved through the composite film prepared by dual-source co-evaporation technique so that the film with higher laser-induced damage threshold than that of single component film can be obtained.