Symmetrical periods used as matching layers in multilayer thin film design

Properties of symmetrical layers as matching layers in multilayer thin film design were analyzed. A calculation method was presented to derive parameters of desired equivalent refractive index. A harmonic beam splitter was designed and fabricated to test this matching method.     

表面热透镜薄膜吸收测量灵敏度提高方法

为提高表面热透镜薄膜吸收测量仪的灵敏度，在表面热透镜衍射理论基础上，通过数值模拟给出了探测激光腰斑半径、探测激光腰斑到样品表面距离、样品到探测光纤端面距离等仪器参数的优化方法. 经优化调整后该仪器能达到优于0.1ppm量级的薄膜吸收率测量灵敏度. 关键词： 吸收测量 表面热透镜 光热形变 薄膜     

沉积温度对LaF3薄膜性能的影响

 在189，255，277和321 ℃的沉积温度下用热舟蒸发方法制备了LaF₃薄膜。通过X射线衍射(XRD)测试了薄膜的晶体结构;采用分光光度计测量了薄膜的透射光谱，并计算得到样品的折射率、消光系数和截止波长;利用光学干涉仪测试得到了薄膜的残余应力;采用三倍频Nd:YAG脉冲激光测试了薄膜的激光损伤阈值。结果表明：随沉积温度的提高，LaF₃薄膜的结晶状况明显变好，晶粒尺寸逐渐变大；膜层变得更加致密，折射率变大，然而薄膜吸收变得严重，截止波段向长波漂移，同时薄膜的残余应力也增加，内应力在薄膜的残余应力中起着决定作用；薄膜的激光损伤阈值在高温制备时相对较高。     

薄膜体内缺陷对损伤概率的影响

由实验中得到的激光损伤概率与表面杂质密度的关系出发，结合XRD测试和激光损伤测试的结果，得到体缺陷或杂质破坏起主导作用的损伤机理.将激光作用时杂质吸收的热学和力学过程与杂质分布的统计规律结合起来，得到了深埋于薄膜内部的杂质诱导薄膜损伤概率与杂质密度、激光功率密度以及薄膜厚度的关系.该模型认为能诱导薄膜破坏的杂质尺寸范围与杂质填埋深度有关，所以不同深度处能诱导薄膜损伤的杂质密度不一样，理论结果与实验结果符合得很好.该理论模型还可以很好地解释损伤形貌.     

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.     

Laser induced damage of multi-layer dielectric used in pulse compressor gratings

Laser induced damage threshold (LIDT) of multi-layer dielectric used in pulse compressor gratings (PCG) was investigated. The sample was prepared by e-beam evaporation (EBE). LIDT was detected following ISO standard 11254-1.2. It was found that LIDTs of normal and 51.2°incidence (transverse electric (TE) mode) were 14.14 and 9.31 J/cm2, respectively. A Nomarski microscope was employed to map the damage morphology, and it was found that the damage behavior was pit-concave-plat structure for normal incidence, while it was pit structure for 51.2°incidence with TE mode. The electric field distribution was calculated to illuminate the difference of LIDT between the two incident cases.     

Harmonic beam splitter design and fabrication

Two problems of half-wave hole and high ripples in the transmittance region for a harmonic beam splitter had been pointed out and analyzed. Based on the application of a half-wavelength control and a new admittance matching methods, a harmonic beam splitter was designed and fabricated. The former method eliminated the half-wave hole fundamentally, and the latter smoothed high ripples in the transmittance region effectively. The matching stack consisted of a symmetrically periodic structure and provided a complete matching at the desired wavelength, i.e., both conditions for the equivalent admittance and phase thickness were fulfilled. Furthermore, both the theoretical and the tested curves had been given, and a good agreement between them was obtained.     

高反射硅镜弱吸收的研究

运用表面热透镜技术精确测量 1315nm高反射硅镜的弱吸收 ,并结合原子力显微镜所显示的薄膜表面情况判断引起吸收的原因 ,为工艺上减少吸收降低损耗提供测量保证     

制备超薄多层膜的自动转速控厚法

在转速控厚法的基础上 ,排除了射频溅射的电磁干扰 ,实现了自动转速控厚法。用这种方法镀制超薄多层膜时 ,可以实时记录下镀制每层膜的沉积时间、自动切换转速、完成设定周期后自动停止转动。自动转速控厚法与转速控厚法相比 ,明显降低了多层膜制备的劳动强度 ,提高了多层膜制备的成品率和监控精度。而且将在镀制复杂膜系多层膜时 ,具有更加明显的优势     

全电介质脉宽压编光栅的研究进展

超短脉冲超高能量激光器作为研究光和物质相互作用以及惯性约束聚变的手段而得到了广泛的应用.综述了应用于啁啾脉冲放大(CPA)系统的脉冲压缩光栅(PCG)的发展概况;分析和评述了脉宽压缩光栅的设计原理和制作工艺,并给出了脉宽压缩光栅的发展展望.实践和理论证明采用多层膜介质衍射光栅是实现高性能脉宽压缩光栅的一种优良的设计方案.