超低面形宽带高反射薄膜设计及制备技术研究

光学薄膜元件的面形偏差会导致高精度激光系统中传输光束发生波前畸变,严重影响光学设备的性能。传统的面形偏差控制技术是采用双面镀膜,但需要反复抛光基片以获得高精度面形,这会大大增加研制成本,限制该方法的使用。文中基于离子束溅射沉积技术,采用薄膜应力形变模型预测镀膜后面形变化情况,然后对待镀元件的镀膜面预加工出与变形方向相反的面形,来补偿镀膜后膜层应力造成的薄膜元件变形,最后在预加工好的基片上制备超低面形的宽带高反膜,实现了在550~750 nm的工作波长下反射率R≥99.5%,面形PV≤0.15λ@632.8 nm。此项技术是通过标定薄膜材料的力学参数,预测在相同工艺条件下任意多层膜的面形变化,实现在超宽光谱设计的同时引入力学同步设计,制备出满足光、力双重指标的高质量光学薄膜。

Study on the design and preparation technology of ultra-low profile wideband high reflection thin films

The surface shape deviation of the optical thin film element will cause the wavefront distortion of the transmitted beam in the high-precision laser system, which will seriously affect the performance of the optical equipment. The traditional surface profile deviation control technology uses double-sided coating, but it is necessary to repeatedly polish the substrate to obtain a high-precision surface profile, which will greatly increase the development cost and limit the use of this method. Based on ion beam sputtering deposition technology, a stress-deformation model was used to predict the shape change after coating, and then the coating surface of the component to be plated was pre-processed into a surface shape opposite to the deformation direction, compensating for the deformation of thin film components caused by the stress of the film after coating. Finally, an ultra-low-profile broadband high-reflection film was prepared on the pre-processed substrate to achieve reflectivity R≥99.5% and PV≤0.15λ@632.8 nm at the working wavelength of 550-750 nm. Through calibrating the mechanical parameters of thin film materials, this technology predicts the surface shape changes of any multilayer film under the same process conditions, realizes the introduction of mechanical synchronization design while designing the ultra-wide spectrums, and prepares high-quality optical films that meet the dual indicators of light and force.