Comparison of TiO2 and ZrO2 films deposited by electron-beam evaporation and by sol-gel process

TiO2 and ZrO2 films are deposited by electron-beam (EB) evaporation and by sol-gel process. The film properties are characterized by visible and Fourier-transform infrared spectrometry, x-ray diffraction analysis, surface roughness measure, absorption and laser-induced damage threshold (LIDT) test. It is found that the sol-gel Elms have lower refractive index, packing density and roughness than EB deposited films due to their amorphous structure and high OH group concentration in the film. The high LIDT of sol-gel films is mainly due to their amorphous and porous structure, and low absorption. LIDT of EB deposited film is considerably affected by defects in the Elm, and LIDT of sol-gel deposited film is mainly effected by residual organic impurities and solvent trapped in the film.

Influences of annealing on residual stress and structure of HfO2 films

HfO2 Elms are deposited on BK7 glass substrates by electron beam evaporation. The influences of annealing between 100 degrees C and 400 degrees C on residual stresses and structures of HfO2 films are studied. It is found that little differences of spectra, residual stresses and structures are obtained after annealing at lower temperatures. After annealing at higher temperatures, the spectra shift to short wavelength, the residual stress increases with the increasing annealing temperature. At the same time, the crystallite size increases and interplanar distance decreases. The variations of optical spectra and residual stress correspond to the evolutions of structures induced by annealing.

Influence of annealing temperature on structure, optical loss and laser-induced damage threshold of TiO2 thin films

TiO2 thin films are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for 4h, the spectra and XRD patterns of the TiO2 thin film are obtained. Weak absorption of coatings is measured by the surface thermal lensing technique, and laser-induced damage threshold (LIDT) is determined. It is found that with the increasing annealing temperature, the transmittance of TiO2 films decreases. Especially when coatings are annealed at high temperature over 1173K, the optical loss is very serious. Weak absorption detection indicates that the absorption of coatings decreases firstly and then increases, and the absorption and defects play major roles in the LIDT of TiO2 thin films.

Comparison of femtosecond and nanosecond laser-induced damage in HfO2 single-layer film and HfO2-SiO2 high reflector

HfO2 single layers, 800 run high-reflective (HR) coating, and 1064 ran HR coating were prepared by electron-beam evaporation. The laser-induced damage thresholds (LIDTs) and damage morphologies of these samples were investigated with single-pulse femtosecond and nanosecond lasers. It is found that the LIDT of the HfO2 single layer is higher than the HfO2-SiO2 HR coating in the femtosecond regime, while the situation is opposite in the nanosecond regime. Different damage mechanisms are applied to study this phenomenon. Damage morphologies of all samples due to different laser irradiations are displayed. (c) 2007 Optical Society of America.

Preparation of high laser induced damage threshold antireflection film using interrupted ion assisted deposition

Single layers and antireflection films were deposited by electron beam evaporation, ion assisted deposition and interrupted ion assisted deposition, respectively. Antireflection film of quite high laser damage threshold (18J/cm(2)) deposited by interrupted ion assisted deposition were got. The electric field distribution, weak absorption, and residual stress of films and their relations to damage threshold were investigated. It was shown that the laser induced damage threshold of film was the result of competition of disadvantages and advantages, and interrupted ion assisted deposition was one of the valuable methods for preparing high laser induced damage threshold films. (c) 2007 Optical Society of America

Optimization of thin-film design for multi-layer dielectric grating

Thin-film design used to fabricate multi-layer dielectric (MLD) gratings should provide high transmittance during holography exposure, high reflectance at use wavelength and sufficient manufacturing latitude of the grating design making the MLD grating achieve both high diffraction efficiency and low electric field enhancement. Based on a (HLL)H-9 design comprising of quarter-waves of high-index material and half-waves of low-index material, we obtain an optimum MLD coating meeting these requirements by inserting a matching layer being half a quarter-wave of Al2O3 between the initial design and an optimized HfO2 top layer. The optimized MLD coatings exhibits a low reflectance of 0.017% under photoresist at the exposure angle of 17.8 degrees for 413 nm light and a high reflectance of 99.61% under air at the use angle of 51.2 degrees for 1053 nm light. Numerical calculation of intensity distribution in the photoresist coated on the MLD film during exposure shows that standing-wave patterns are greatly minimized and thus simulation profile of photoresist gratings after development demonstrates smoother shapes with lower roughness. Furthermore, a MLD gratings with grooves etched into the top layer of this MLD coating provides a high diffraction efficiency of 99.5% and a low electric field enhancement ratio of 1.53. This thin-film design shows perfect performances and can be easily fabricated by e-beam evaporation. (c) 2006 Elsevier B.V. All rights reserved.

利用等效层的消偏振宽带减反膜设计

分析了倾斜入射条件下导致光学薄膜产生偏振的原因, 针对不同偏振态的等效导纳与等效相位进行了分析, 并计算了对称膜层在45°入射条件下不同偏振态的等效折射率与等效相位厚度, 采用等效层方法设计了光学性能良好的600～900 nm波段消偏振宽带减反膜。最后利用电子束蒸发技术制备了薄膜样品, 样品的光谱性能完全能够满足使用要求。其中在600～900 nm波段范围内, 平均反射率均小于1.38%, 反射率的偏振度均低于0.89％。另外, 通过对其理论及实验光学性能、角度敏感性、膜层厚度误差敏感性等方面的分析结果可

三倍频分光膜在1064 nm的破斑特性研究

采用电子束蒸发方式制备了两种不同材料组合的分光膜,分别对其在波长1064 nm激光辐照下的损伤阈值进行了测试,用Alpha-Step 500台阶仪对破斑进行了深度测量。实验结果表明,破斑呈现出表面层的剥落和深坑破坏两种形态。表面层的剥落深度在一定范围内不随能量密度的变化而变化；深坑破坏深浅不一,是膜内缺陷融化、汽化及喷发的综合作用的结果,是损伤阈值降低的主要原因。

光学薄膜膜厚自动控制系统的研究

介绍了一种利用光电极值法同时控制规整膜系和非规整膜系的方法,利用VC＋＋编写程序实现对光学监控信号的采集、处理及停镀点的自动判断,实现了规整膜系和非规整膜系膜层厚度的自动控制.并利用该膜厚自动控制系统实验制备了规整膜系和非规整膜系多层膜,实验结果表明：利用该系统镀制的薄膜重复性良好,且光谱曲线和理论光谱曲线吻合较好.该系统解决了非规整膜系的监控问题,由计算机控制膜层的停镀点,排除了人的主观因素对薄膜的性能及其制备的重复性产生的影响,提高了薄膜镀制的重复性和成品率.

LBO晶体上具有不同厚度过渡层的倍频增透膜的设计和制备

Design and preparation of frequency doubling antireflection coating with different thicknesses of interlayer were investigated for LiB₃O₅ (LBO) substrate. The design was based on the vector method. The thickness of the inserted SiO₂ interlayer could be changed in a wide range for the four-layer design with two zeros at 1064 and 532 nm. The coatings without any interlayer and with 0.1 quarter-wave (λ/4), 0.3 λ/4, 0.5 λ/4 SiO₂ interlayer were deposited respectively on LBO by using electron beam evaporation technique. All the prepared coatings with SiO₂ interlayer indicated satisfying optical behavior. This expanded our option for the thickness of an interlayer when coating on LBO substrate. The prepared films with SiO₂ interlayer showed better adhesion than that without any interlayer. The thickness of the interlayer affected the adhesion, the adhesion for the coating with 0.5 λ/4 SiO₂ interlayer was not as good as the other two.}

LBO晶体上1064，532nm倍频增透膜的镀制及性能分析

用电子束蒸发沉积方法在X切LBO（X-LBO）晶体上镀制了两种不同膜系结构的1064和532nm倍频增透膜，其中一种膜系结构为基底／ZrO2／Y2O3／A12O3／SiO2／空气，另一种为基底／0．5Al2O3／ZrO2／Y2O3／A12O3／SiO2／空气，两种膜系结构的主要差别在于有无氧化铝过渡层。测量了薄膜的反射率光谱曲线，发现两种增透膜在1064和532nm处的反射率均小于0．5％，实际镀制结果与理论设计曲线的差异主要是由材料折射率的变化引起的。且对样品在空气环境中进行了温度为473K的退火处理，

沉积温度对LaF3薄膜性能的影响

abstract {LaF₃ single-layer coatings were prepared by thermal boat evaporation at the deposition temperatures of 189, 255, 277 and 321°C respectively. The crystal structures of the coatings were characterized by X-ray diffraction (XRD). A spectrophotometer was employed to measure its transmittance. Moreover, refractive index, extinction coefficient and cut-off wavelength were obtained from the measured transmittance spectral curve. The residual stress was evaluated by the Stoney's equation and optical interferometer. Laser induce damage threshold (LIDT) was performed by a tripled Nd:YAG laser system. The results show that the crystallization status becomes better with the deposition temperature increasing. Correspondingly, the grain size also gets larger. Meanwhile, the coatings become more compact and the refractive index increases. However, the absorption of coatings seriously rises and the cut-off wavelength drifts to the long wave. In addition, the residual stress also increases and the intrinsic stress plays a determinant role in the coating. The LIDT of the coating also enhances at high temperature.}

渐变折射率薄膜的分层评价探讨

首先阐述了将渐变折射率薄膜细分为多层均匀薄膜的分层介质理论，接着给出了一种获得最佳分层数目的分层评价方法，最后以线性变化渐变折射率薄膜为例说明了如何优化获得渐变折射率薄膜的分层数目．研究发现：渐变折射率薄膜的分层数目与薄膜的厚度和薄膜的折射率变化快慢有关，在一定的折射率变化范围内，渐变折射率薄膜的分层数目随着薄膜厚度的增加先减小后增大．

真空室内金属杂质污染对光学薄膜性能的影响

真空室内金属粒子污染是降低激光薄膜性能的一个重要因素。采用高真空残余气体分析仪,对薄膜沉积过程中的气氛进行分析。发现由黄铜制作的加热灯架在工作时会分解出Zn,在这种条件下沉积薄膜,会使薄膜中掺入金属杂质,导致薄膜激光破坏阈值降低。采用表面分析技术对薄膜的组分进行分析,证实薄膜中锌杂质的存在。激光破坏实验证明,含有锌杂质的薄膜的破坏阈值明显降低。

沉积速率对热舟蒸发LaF3薄膜性能的影响

用热舟蒸发方法在不同的沉积速率下制备了LaF3单层膜,并对部分单层膜进行了真空退火。分别采用X射线衍射(XRD),Lambda 900 光谱仪和355 nm Nd∶YAG脉冲激光测试了薄膜的晶体结构、透射光谱和激光损伤阈值(LIDT),并通过透射光谱计算得到样品的折射率和消光系数。实验结果表明,增大沉积速率有利于LaF3薄膜的结晶和择优生长,可以提高薄膜的致密性和折射率,但薄膜的抗激光损伤能力有所下降;沉积速率太大,又会恶化薄膜的结晶性能,同时薄膜中产生大量孔洞,薄膜的机械强度降低,导致薄膜的折射率减小和