【作者】 郭春；

【导师】 李斌成；

【作者基本信息】 中国科学院研究生院（光电技术研究所） ， 光学工程， 2014， 博士

【摘要】 为满足精密光学系统的性能需求，真空紫外光学薄膜元件的尺寸和数值孔径越来越大，对制备高性能的真空紫外光学薄膜提出更多的挑战。主要包括真空紫外光学薄膜光学常数确定、光学元件薄膜厚度非均匀性校正和膜料沉积角对真空紫外光学薄膜性能影响等方面。本文详细介绍了光度法确定薄膜光学常数。基于光学薄膜折射率随其厚度变化关系，分别建立折射率均匀和折射率非均匀薄膜模型，提出了用于消除基底背面反射光对实测薄膜光谱数据的影响办法，采用光谱包络法确定光学薄膜材料在真空紫外波段的光学常数。仔细阐述真空紫外光学薄膜基底光学常数的获取方法。另外，将带吸收的等效界面层引入光学薄膜光学常数确定中，首次报道了依据薄膜实测光谱数据，使用多参数拟合法同时确定薄膜材料的光学常数和表面均方根粗糙度。与原子力显微镜实测薄膜均方根表面粗糙度比较，证实了本模型的正确性。针对真空镀膜机行星旋转系统的特点，分别建立了未使用和使用修正挡板修正时大尺寸平面/曲面光学元件上沉积光学薄膜厚度模型。详细说明使用计算机辅助完成适用于真空镀膜机行星旋转系统中的修正挡板设计流程，并介绍了两种薄膜材料发射特性的确定办法。全面叙述计算机辅助设计的修正挡板在真空镀膜过程中对大尺寸平面形、凸球形和凸锥形光学元件上光学薄膜厚度非均匀性校正的验证性实验，实验结果证明本文建立的未使用/使用修正挡板时真空镀膜机行星旋转夹具系统中光学元件上沉积的薄膜厚度模型准确性和修正挡板优化设计方法的可靠性。氟化镁是真空紫外波段最常用的薄膜材料，采用热蒸发镀膜工艺制备了不同沉积角下的氟化镁光学薄膜。分别使用紫外-可见分光光谱仪、扫描电镜、原子力显微镜、x射线衍射仪、红外光谱仪等对氟化镁薄膜的光谱性能、剖面微观结构、表面形貌、x射线衍射图谱和红外特征谱进行表征，分析氟化镁薄膜光谱性能和微观结构随薄膜材料沉积角的变化关系。研究结果表明，当前工艺条件下制备的氟化镁薄膜是倾斜圆柱状生长，并且具有多晶结构。随着氟化镁薄膜材料的沉积角增加，热蒸发工艺制备的氟化镁光学薄膜的折射率、聚集密度和晶粒尺寸下降，同时该薄膜的消光系数、总光学损耗、表面粗糙度、缺陷密度和吸附的水含量都增加。另外，还分析了不同沉积角下制备的氟化镁薄膜的光谱老化特性，以及紫外辐照处理对老化后的氟化镁光学薄膜的光学性能提高。更多还原

【Abstract】 With the development of vacuum ultraviolet (VUV) light sources, especially excimer lasers,free electron lasers, and all solid state lasers pumped by semiconductor lasers have shownwidespread potential for a great many applications such as the laser spectrum in VUV,fabrication of micro-electronic devices, precision material processing, and biomedicineengineering. To meet the performance requirements of precision optical systems, the size and thenumerical aperture of the vacuum ultraviolet optical elements is increase. There are morechallenges for the preparation of high-performance vacuum ultraviolet optical coatings,including determination of the optical constants of optical coatings used for the VUV spectralregion, correction of the film thickness non-uniformity deposited on the optical elements and theeffects of deposition angle onto the performances of optical coatings.Determination of the optical constants of thin film by a spectrophotometric method isdescribed in the paper. Based on the variation of the refractive index with the thickness of thinfilm, refractive index homogeneous and inhomogeneous coating models are developed. A newmethod is given to correct the spectrum measurements of thin films to eliminate the effect due tothe reflectance from the rear surface of the substrate. Finally, the optical constants of thin filmare extracted from envelops of the transmittance and/or reflectance spectra based on the models.A simple approach for determining the optical constants of substrate is also described. Moreover,a model taking into account surface roughness of an optical coating according to effectiveabsorbing layer theory has been proposed and applied to determine simultaneously the opticalconstants and surface roughness of the optical coating from spectrophotometric measurements.The determined surface roughness of thin film is in good agreement with atomic forcemicroscope (AFM) measurement.According to the characteristics of a coating machine with a planetary rotation system, themodels of thin films deposited on a large-size flat/curved optical elements without/withshadowing mask have been developed. The progress of the shadowing mask designed withcomputer-aided for the coating machine having a planetary rotation system is described in detail,and two methods has been used to determinate the emission characteristics parameter of thin filmmaterial. Typical experiments for thickness non-uniformity corrections of thin films deposited onthe flat, convex spherical and convex conical substrates with optimized shadowing mask arecomprehensively performed. The experimentally achieved results strongly suggest that the developed thickness models as well as the corresponding shadowing mask design via numericaloptimization work well for the thickness uniformity correction of thin films deposited on variousshaped substrates with large diameters and/or strongly curved surfaces.Magnesium fluoride (MgF2) is a low refractive index material commonly used for VUVoptical coating applications owing to its high transparency in these wavelength ranges. In thepapar, MgF2films deposited by resistive heating evaporation with oblique-angle deposition havebeen investigated in details. The optical and micro-structural properties of single-layer MgF2films were characterized by UV-VIS and FTIR spectrophotometers, scanning electronmicroscope (SEM), AFM, and x-ray diffraction (XRD), respectively. The dependences of theoptical and micro-structural parameters of the thin films on the deposition angle were analyzed.It was found that the MgF2film in a columnar microstructure and polycrystalline. As thedeposition angle increased, the refractive index, packing density and grain size of the MgF2filmsdecreased, while the extinction coefficient, optical loss, root-mean-square (rms) roughness,dislocation density and adsorbed water content increased. Furthermore, the spectral agingcharacteristics of MgF2thin films prepared under different deposition angles are investigated.The improvement of the optical performances of the MgF2thin films treated by UV irradiationhas been proved.更多还原