杂质对溶胶-凝胶SiO2薄膜激光损伤的影响

 采用溶胶-凝胶法制备了含有吸收性杂质和非吸收性杂质的SiO₂增透膜,采用波长为1 064 nm的激光对其进行了小光斑激光预处理,对比研究了预处理前后的激光损伤差异,研究表明：激光预处理对于洁净的SiO₂薄膜影响不大;含10 μm SiO₂颗粒杂质的样品微透镜效应很明显,容易成为损伤起始的种子,激光预处理后情况有所改善;含有CeO₂颗粒杂质的样品表现出了很强的吸收性质,损伤阈值降低到不足洁净样品的一半。所有样品激光预处理后损伤形貌未发生变化,透光率峰值均有约50 nm的蓝移。     

化学法制备的HfO2薄膜的激光损伤阈值研究

 采用化学法制备了HfO₂介质膜，研究了热处理、紫外辐照以及Al₂O₃复合对HfO₂介质膜激光损伤阈值的影响。采用红外光谱（FTIR）和X射线衍射仪对薄膜进行了表征，并用输出波长为1.064 μm、脉宽为10 ns的电光调Q激光系统测试薄膜的激光损伤阈值。实验结果表明：采用150 ℃左右的温度对薄膜进行热处理可以提高薄膜的激光损伤阈值，所获得的薄膜的激光损伤阈值高达42.32 J/cm²，比热处理前的激光损伤阈值提高了82%；无机材料Al₂O₃的适量添加能够提高薄膜的激光损伤阈值，其中HfO₂与Al₂O₃的最佳质量配比约为95∶5；另外，对薄膜进行适当的紫外辐照也可改善HfO₂ 薄膜以及HfO₂-Al₂O₃复合薄膜的抗激光损伤性能。紫外辐照对提高HfO₂-Al₂O₃复合薄膜的激光损伤阈值效果尤为显著，辐照40 min后的激光损伤阈值达到44.33 J/cm²，比紫外辐照前的激光损伤阈值提高了90%。     

HfO2/SiO2双色膜在1 064 nm和532 nm激光辐照下的损伤特性

 采用电子束蒸发的方式,制备了有氧化硅内保护层和没有氧化硅内保护层的1 064 nm高透过、532 nm高反射的HfO₂/SiO₂双色膜,测量了它们的光学性能以及在基频和倍频激光辐照下的抗损伤性能。结果表明:氧化硅内保护层提高了双色膜在基频光辐照下的损伤阈值,对双色膜在倍频光辐照下的损伤阈值无明显影响。通过观察薄膜的损伤形貌,分析破斑的深度信息结合驻波场分布,对两类双色膜在基频光和倍频光下的损伤机制做了初步探讨。分析表明:氧化硅内保护层提高了膜基界面的抗损伤性能,从而提高了双色膜在基频光下的损伤阈值。     

层间热处理对SiO2/ZrO2双层膜的影响

 以正硅酸乙酯和丙醇锆为前驱体,用溶胶-凝胶法在K9基片上提拉镀制SiO₂/ZrO₂双层膜。采用不同实验步骤制备了2个样品,样品1镀完SiO₂后直接镀ZrO₂ ,样品2镀完SiO₂经热处理后再镀ZrO₂。采用原子力显微镜、椭偏仪、紫外-可见分光光度计对薄膜进行表征。针对SiO₂/ZrO₂双层膜,考虑到膜间渗透的影响,采用３层Cauchy模型进行椭偏模拟,椭偏参数的模拟值曲线与椭偏仪的测量值曲线十分吻合,进而发现热处理可以使SiO₂/ZrO₂双层膜之间的渗透减少近23 nm,从而提高其峰值透射率。利用输出波长1.064 mm,脉宽8.1 ns的激光束对样品进行了损伤阈值的测试,用光学显微镜观察损伤形貌,结果发现两者损伤阈值分别为13.6 J/c2和14.18 J/cm²,均为膜的本征损伤。     

物理法和化学法制备的单层ZrO2膜的激光损伤行为差异

 分别采用电子束热蒸发技术和溶胶-凝胶技术在K9基片上镀制了光学厚度相近的ZrO₂单层薄膜,测试了两类薄膜的激光损伤阈值。分别采用透射式光热透镜技术、椭偏仪、原子力显微镜和光学显微镜研究了两类薄膜的热吸收、孔隙率、微观表面形貌、激光辐照前薄膜的杂质和缺陷状况以及激光辐照后薄膜的损伤形貌。实验结果表明：两类薄膜的不同损伤形貌与薄膜的热吸收与微观结构有关， 物理法制备的ZrO₂膜结构致密紧凑，膜层的杂质和缺陷多；化学法制备的ZrO₂膜结构疏松多孔，膜层纯净杂质少，激光损伤阈值达26.9 J/cm²；因物理法制备的ZrO₂膜拥有更大的热吸收(115.10×10^-6)和更小的孔隙率(0.20)，其激光损伤阈值较小(18.8 J/cm²)，损伤主要为溅射和应力破坏，而化学法制备的ZrO₂膜的损伤主要为剥层。理论上对实验结果进行了解释。     

多孔TiO2/Al/SiO2纳米复合结构的紫外光吸收特性研究

在SiO₂玻璃衬底上用脉冲激光沉积(PLD)技术，分别沉积Ti和Ti/Al膜，经电化学阳极氧化成功制备了多孔TiO₂/SiO₂和TiO₂/Al/SiO₂纳米复合结构. 其中TiO₂薄膜上的微孔阵列高度有序，分布均匀. 实验研究了Al过渡层对多孔TiO₂薄膜光吸收特性的影响. 结果表明：无Al过渡层的多孔TiO₂薄膜其紫外吸收峰在27     

溶胶-凝胶SiO2酸性膜与碱性膜的激光损伤行为

 采用溶胶-凝胶技术分别在K9基片上镀制了光学厚度相近的单层SiO₂酸性膜和碱性膜。测试了两类薄膜的激光损伤阈值;分别采用透射式光热透镜技术、椭偏仪、原子力显微镜、扫描电镜和光学显微镜研究了两类薄膜的热吸收、孔隙率、微观表面形貌、激光辐照前薄膜的杂质和缺陷状况以及激光辐照后薄膜的损伤形貌。实验结果表明：相对于碱性膜,酸性膜有更大的热吸收和更小的孔隙率,因此其激光损伤阈值较小;两类薄膜不同的损伤形貌与薄膜的热吸收系数与微观结构有关。     

用1064nm激光增强HfO2/SiO2薄膜的抗激光损伤能力的实验研究

 用1 064nm激光实验研究了HfO₂/SiO₂薄膜的激光损伤增强效应，实验以薄膜激光损伤阈值70%的激光能量开始，采用N-ON-1方式处理薄膜，激光脉冲的能量增量为5J/cm²。实验结果表明，激光处理薄膜表面能使激光损伤阈值平均提高到3倍左右，并且薄膜的损伤尺度也明显减小。对有缺陷的薄膜，其缺陷经低能量激光后熔和消除，其抗激光损伤能力得到增强，但增强得并不显著，而薄膜本身的激光预处理，可以使其激光损伤阈值大大提高。     

高抗激光损伤阈值介孔SiO2 减反射膜

 用P123作模板剂,通过正硅酸乙酯的水解缩聚和溶剂蒸发自组装过程在K9玻璃上制备介孔SiO₂膜。应用FT-IR,XRD,N₂ 吸附-脱附,AFM和UV-Vis表征手段研究了薄膜的介孔结构和光学性能,并使用“R-on-1”模式,以Nd:YAG脉冲激光（9.2 ns, 1 064 nm）测试了薄膜的激光损伤阈值。结果表明:所镀制单层介孔SiO₂膜具有规整的2D p6 mm长周期结构,为SBA-15型,膜层表面比较平整（均方根粗糙度为2.923 nm）,在1 064 nm处的透过率为99.5%, 换算为激光脉宽为1 ns时,膜层的激光损伤阈值为21.6 J/cm²,显示出了较好的减反性能和抗激光损伤性能。     

SiO2半波覆盖层对HfO2/SiO2高反膜激光损伤的影响

 研究了SiO₂半波覆盖层对HfO₂/SiO₂高反射膜1064nm激光损伤的影响,分析薄膜的激光损伤特性及图貌得出, 对于单脉冲（1-ON-1）激光损伤,SiO₂半波覆盖层能提高HfO₂/SiO₂高反膜的激光损伤阈值;可显著降低激光损伤程度,减小灾难性损伤发生的概率;可大幅度提高HfO₂/SiO₂高反膜膜的抗激光损伤能力。     

Enhanced laser induced damage threshold of dielectric antireflection coatings by the introduction of one interfacial layer

A new method for increasing laser induced damage threshold (LIDT) of dielectric antireflection (AR) coating is proposed. Compared with AR film stack of H2.5L (H:HfO2, L:SiO2) on BK7 substrate, SiO2 interfacial layer with four quarter wavelength optical thickness (QWOT) is deposited on the substrate before the preparation of H2.5L film. It is found that the introduction of SiO2 interfacial layer with a certain thickness is effective and flexible to increase the LIDT of dielectric AR coatings. The measured LIDT is enhanced by about 50%, while remaining the low reflectivity with less than 0.09% at the center wavelength of 1064 nm. Detailed mechanisms of the LIDT enhancement are discussed.     

Study on high-reflective coatings of different designs at 532 nm

Conventional HfO2/SiO2 and Al2O3/HfO2/SiO2 double stack high reflective （HR） coatings at 532 nm are deposited by electron beam evaporation onto BK7 substrates. The laser-induced damage threshold （LIDT） of two kinds of HR coatings is tested, showing that the laser damage resistance of the double stack HR coatings （16 J/cm2） is better than that of the conventional HR coatings （12.8 J/cm2）. Besides, the optical properties, surface conditions, and damage morphologies of each group samples are characterized. The results show that laser damage resistance of conventional HR coatings is determined by absorptive defect, while nodular defect is responsible for the LIDT of double stack HR coatings.     

Postprocessing treatments to improve the laser damage resistance of fused silica optical surfaces and SiO2 coatings

The combination of deep wet etching and a magneto-rheological finishing(MRF) process is investigated to simultaneously improve laser damage resistance of a fused-silica surface at 355 nm. The subsequently deposited SiO2 coatings are researched to clarify the impact of substrate finishing technology on the coatings. It is revealed that a deep removal proceeding from the single side or double side had a significant impact on the laser-induced damage threshold(LIDT) of the fused silica, especially for the rear surface. After the deep etching, the MRF process that followed does not actually increase the LIDT, but it does ameliorate the surface qualities without additional LIDT degradation. The combination guarantee both the integrity of the surface’s finish and the laser damage resistance of the fused silica and subsequent SiO2 coatings.     

Accumulation effect of SiO_2 protective layer on multi-shot laser-induced damage in high-reflectivity HfO_2/SiO_2 coatings

The accumulation effects in high-reflectivity(HR) HfO2/SiO2 coatings under laser irradiation are investigated.The HR HfO2/SiO2 coatings are prepared by electron beam evaporation at 1 064 nm.The laser-induced damage threshold(LIDT) are measured at 1 064 nm and at a pulse duration of 12 ns,in 1-on-1 and S-on-1 modes.Multi-shot LIDT is lower than single-shot LIDT.The laser-induced and native defects play an important role in the multi-shot mode.A correlative theory model based on critical conduction band electron density is constructed to elucidate the experimental phenomena.     

Comparison of laser-induced damage in Ta2O5 and Nb2O5 single-layer films and high reflectors

Ta2O5 and Nb2O5 films are deposited on BK7 glass substrates using an electron beam evaporation method and are annealed at 673 K in the air.In this letter,comparative studies of the optical transmittance,microstructure,chemical composition,optical absorption,and laser-induced damage threshold(LIDT) of the two films are conducted.Findings indicate that the substoichiometric defect is very harmful to the laser damage resistance of Ta2O5 and Nb2O5 films.The decrease of absorption improves the LIDT in films deposited by the same material.However,although the absorption of the Ta2O5 single layer is less than that of the Nb2O5 single layer,the LIDT of the former is lower than that of the latter.High-reflective(HR) coatings have a higher LIDT than single layers due to the thermal dissipation of the SiO2 layers and the decreased electric field intensity(EFI).In addition,the Nb2O5 HR coating achieves the highest LIDT at 25.6 J/cm 2 in both single layers and HR coatings.     

Influence of Vacuum Organic Contaminations on Laser-Induced Damage of 1064 nm Anti-Reflective Coatings

We investigate the influence of vacuum organic contaminations on laser-induced damage threshold （LIDT） of optical coatings. Anti-reflective （AIR） coatings at 1064 nm made by Ta2 O5/SiO2 are deposited by the ion beam sputtering method. The LIDTs of AR coatings are measured in vacuum and in atmosphere, respectively. It is exhibited that contaminations in vacuum are easily to be absorbed onto optical surface because of lower pressure, and they become origins of damage, resulting in the decrease of LIDT from 24.5J/cm^2 in air to 15.TJ/cm^2 in vacuum. The LIDT of coatings in vacuum has is slightly changed compared with the value in atmosphere after the organic contaminations are wiped off. These results indicate that organic contaminations are the main reason of the LIDT decrease in vacuum. Additionally, damage morphologies have distinct changes from vacuum to atmosphere because of the differences between the residual stress and thermal decomposability of filmy materials.     

单发大口径光束下介质膜损伤阈值测试

针对传统的激光诱导损伤阈值测试中存在的耗时问题,提出了一种利用单发次、大口径光束的介质膜损伤阈值的快速测定方法。该方法以图像处理为基础,通过坐标变换和栅格压缩,建立了样品辐照区域内损伤分布与光斑强度分布之间的精确对应关系。基于对大口径光斑辐照区域内损伤信息的快速提取和统计方法,通过单次激光辐照,获取了待测区域的损伤阈值。根据此方法搭建了单发大口径光束损伤阈值测试平台,并对HfO2/SiO2高反射膜损伤阈值进行了单发次测定的验证。     

Impact of organic contamination in vacuum on laser-induced damage threshold of TiO2/SiO2 dielectric mirrors

The influence of organic contamination in vacuum on the laser-induced damage threshold (LIDT) of coatings is studied. TiO2/SiO2 dielectric mirrors with high reflection at 1064 nm are deposited by the electronbeam evaporation method and their LIDTs are measured in vacuum and atmosphere, respectively.It is found that the contamination in vacuum is easily attracted to optical surfaces because of the low pressure and becomes the source of damage, O2 molecules in vacuum with contamination can accelerate the laser-induced damage by observing LIDT and damage morphologies. LIDTs of mirrors have a little change in vacuum compared with in atmosphere when the organic contamination is wiped off. The results indicate that organic contamination is a significant reason to decrease the LIDT in vacuum.     

Effect of SiO2 protective layer on the femtosecond laser-induced damage of HfO2/SiO2 multilayer high-reflective coatings

Two kinds of HfO₂/SiO₂ 800 nm high-reflective (HR) coatings, with and without SiO₂ protective layer were deposited by electron beam evaporation. Laser-induced damage thresholds (LIDT) were measured for all samples with femtosecond laser pulses. The surface morphologies and the depth information of all samples were observed by Leica optical microscopy and WYKO surface profiler, respectively. It is found that SiO₂ protective layer had no positive effect on improving the LIDT of HR coating. A simple model including the conduction band electron production via multiphoton ionization and impact ionization is used to explain this phenomenon. Theoretical calculations show that the damage occurs first in the SiO₂ protective layer for HfO₂/SiO₂ HR coating with SiO₂ protective layer. The relation of LIDT for two kinds of HfO₂/SiO₂ HR coatings in calculation agrees with the experiment result.