自组装法制备的亚波长纳米多孔二氧化硅薄膜

Sub-wavelength nano-porous silica anti-reflection coatings fabricated by dip coating method

通过自组装技术在玻璃基底上制备了二氧化硅薄膜的亚波长多孔结构,这种类似于多晶的胶体晶体结构其特征尺寸约为90nm,通过不同的提拉速度可以实现可见到红外不同波段的增透。系统研究了胶体乳液浓度、基片提拉速度对亚波长多孔薄膜透射谱的影响,探索了在不同波段实现高效率增透的最佳制备条件。通过等效介质理论(EMT)分析了这种亚波长多孔薄膜的光学特性,结果表明控制亚波长多孔结构的占空比可以改变等效膜层的折射率实现高效率增透。通过扫描电镜(SEM)表征了多孔膜的表面形貌,并通过图像处理的方式得到二氧化硅纳米粒子的占空比因子。实验结果表明:在一定范围内,提拉速度不同,对应的等效膜层的折射率会不同,膜层的透射率也不同。组装这种亚波长多孔纳米微结构最高增透率达到99.8%,且具有一定的宽带增透效果,通过控制膜层的厚度可以实现从可见光到红外波段的有效调谐,其在1 064nm处的损伤阈值为21.74J/cm2。

A subwavelength porous structure for SiO2anti-reflection coatings was fabricated on a glass substrate by dip coating method,which has a feature size of 90 nm and could be tuned the maxtransmission wavelength from visible to infrared regions by different withdraw velocities.The effects of colloidal emulsion concentration and substrate lift velocity on the transmission spectrum of the subwavelength porous coating were researched and the best fabrication method for high efficiency antireflection in different wavelengths was explored.On the basis of effective medium theory（EMT）,the optical properties of the sub-wavelength nano-porous silica antireflection coating were analyzed.The results show that the control of duty ratio of subwavelength porous structure can change the refractive index of equivalent membrane layer and can realize the high efficiency anti-reflection.The surface topography of the porous SiO2 anti-reflection coating was characterized by a scanning electron microscopy and the duty ratio of SiO2 nanometer-particles was obtained by image processing.Theresearch results indicate that different lifting speeds will obtain corresponding equivalent coatings with different refractive indexes and different transmitting indexes in a certain range. The maxtransmission efficiency through the substrate of the sub-wavelength nanometer porous silica coating is increased to 99.8%.By controlling the thickness of coating layer,the effective turning implements from visible to infrared regions,and the Nd：YAG laser damage threshold of the antireflection coating exceeds 21.74J/cm2 at 1 064 nm.