Growth and spectral properties of Yb,Tm:YAG crystal

The YAG crystal codoped with Yb3+ and Tm3+ has been grown by Czochralski (Cz) method. The crystal structure of the crystal has been determined by X-ray diffraction analysis. The absorption and emission spectra of Yb,Tm:YAG crystal at room temperature have also been studied. The emission cross-sections have been calculated by Fuechtbauer-Ladenburg formula and reciprocity method. (C) 2007 Elsevier B.V. All rights reserved.

应用离子后处理技术提高薄膜激光损伤阈值

利用电子束热蒸发方法在K9玻璃基底上沉积氧化锆薄膜,并对其中一些样品用低能O2^+进行了后处理.采用表面热透镜技术测量薄膜样品表面弱吸收,采用显微镜观察样品离子后处理前后的显微缺陷密度.测试结果表明:经离子后处理样品表面的缺陷密度从18.6/mm^2降低到6.2/mm^2,且其激光损伤阈值从15.9 J/cm^2提高到23.1 J/cm^2,样品的平均吸收率从处理前的1.147×10^-4降低到处理后的9.56×10^-5.通过对处理前后样品的表面微缺陷密度、吸收率及损伤形貌等的分析发现:离子后处理可以降

氧分压对ZrO2薄膜激光损伤阈值的影响

在不同的氧分压下用电子束热蒸发的方法制备了ZrO2薄膜。分别通过X射线衍射、光学光谱、热透镜技术、抗激光辐照等测试，对所制备样品的微结构、折射率、吸收率及激光损伤阈值进行了测量。实验结果表明，薄膜中晶粒主要是四方相为主的多晶结构，并且随着氧分压的增加，结晶度、折射率以及弱吸收均逐渐降低。薄膜的激光损伤阈值开始随着氧分压增加从18．5J／cm^2逐渐增加，氧分压为9×10^-3Pa时达到最大，值为26．7J／cm^2，氧分压再增加时则又降低到17．5J／cm^2。由此可见，氧分压引起的薄膜微结构变化是ZrO

Influence of negative ion element impurities on laser induced damage threshold of HfO2 thin film

Negative ion element impurities breakdown model in HfO2 thin film was reported in this paper. The content of negative ion elements were detected by glow discharge mass spectrum analysis (GDMS); HfO2 thin films were deposited by the electron-beam evaporation method. The weak absorption and laser induced damage threshold (LIDT) of HfO2 thin films were measured to testify the negative ion element impurity breakdown model. It was found that the LIDT would decrease and the absorption would increase with increasing the content of negative ion element. These results indicated that negative ion elements were harmful impurities and would speed up the damage of thin film. (c) 2006 Elsevier B.V. All rights reserved.

Study of Al2O3/MgF2 HR coatings at 355 nm

With the present work we tried to study the effective methods to improve the laser-induced damage threshold (LIDT) and reflectance of HR coatings at 355 nm. The work presented in this paper wits part of an ongoing study about vacuum annealing. It was dedicated to study the effects Of Vacuum annealing with different temperature gradients on the structure, optical properties and laser-induced damage threshold (LIDT) of 355nm Al2O3/MgF2HR coatings. A number of samples were prepared by electron beam evaporation using the same deposition process with an optimal deposition temperature of 280 degrees C. After deposition, samples were annealed in the coating chamber for 3 h with different temperature gradients. Morphologies of the samples were observed by Leica-DMRXE. Microscope, Structure of the samples had been characterized by X-ray diffraction (XRD). Transmittance and reflectance of the samples were measured by Lambda 900 Spectrometer, The LIDT of the samples was measured by a 355 nm Nd:YAG laser with a pulse width of 8 ns. It was found that the temperature gradient of vacuum annealing had significant effects on the morphology, structure, absorption, and LIDT of the samples, (c) 2005 Elsevier Ltd. All rights reserved.

高真空室中的水蒸气对HfO2薄膜性能的影响

本文研究了在镀膜过程中真空室内水蒸气的含量对HfO2薄膜物理性能的影响。用电子束蒸发和光电极值监控的方法在BK7基底上制备HfO2薄膜。利用残余气体分析仪在线监测了真空室内的残余气氛组成。分别用Lambda 900光谱仪、X射线衍射方法、表面热透镜技术和1064nm的激光器测试了薄膜的光学性能、微结构、吸收和激光损伤阈值。实验发现，附加冷阱装置有助于我们有效控制镀膜过程中的水汽含量，且在水蒸气含量较少的真空室内镀制的薄膜具有较高的折射率，较小的晶粒尺寸，较低的弱吸收值和较高的损伤阈值。

用于掺钛蓝宝石激光系统的高反膜的激光损伤

用电子束蒸发制备了用于掺钛蓝宝石啁啾脉冲放大激光系统的TiO2/HfO2/SiO2高反膜，其带宽约为176nm（R>98%, λ0=800nm），激光损伤阈值（LIDT）为2.4 J/cm2。通过TiO2和HfO2单层膜的透过光谱计算了这两种材料的折射率和消光系数。高反膜的性能主要由高折射率材料决定：折射率越高，反射带越宽；消光系数越小，薄膜吸收越小，LIDT越高。最后，讨论了高反膜的激光损伤机制。

Effect of process parameters on laser damage threshold of TiO2 coatings

We investigate the laser damage behaviour of an electron-beam-deposited TiO2 monolayer at different process parameters. The optical properties, chemical composition, surface defects, absorption and laser-induced damage threshold (LIDT) of Elms are measured. It is found that TiO2 Elms with the minimum absorption and the highest LIDT can be fabricated using a TiO2 starting material after annealing. LIDT is mainly related to absorption and is influenced by the non-stoichiometric defects for TiO2 films. Surface defects show no evident effects on LIDT in this experiment.

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

两种后处理方法对HfO2薄膜性能的影响

利用电子束蒸发和光电极值监控技术制备了氧化铪薄膜，并分别用两种后处理方法（空气中退火和氧等离子体轰击）对样品进行了处理．然后，对样品的透过率、吸收和抗激光损伤阈值进行了测试分析．实验结果表明，两种后处理方法都能不同程度地降低了氧化铪薄膜的吸收损耗、提高了抗激光损伤阈值．实验结果还表明，氧等离子体轰击的后处理效果明显优于热退火，样品的吸收平均值在氧等离子体后处理前后分别为34．8ppm和9．0ppm，而基频（1 064nm）激光损伤阈值分别为10．0J／cm^2和21．4J／cm^2．

三种不同后处理方式对ZrO_2薄膜性能的影响

采用有氧热处理、激光预处理和离子后处理三种方式对电子束蒸发(EBE)制备的单层ZrO_2薄膜进行了后处理,并分别对样品的光学性能和抗激光损伤阈值(LIDT)特性进行了研究。实验结果表明,热处理方式可以有效排除膜层内吸附的水气,弥补薄膜制备过程中的氧损失,使得光谱短移、吸收减小、损伤阈值增高;激光预处理过程可以在一定程度上减少缺陷、提高损伤阈值,但对膜层的光谱和吸收情况没有明显的改善作用;而离子后处理能够提高膜层的堆积密度、减少缺陷、降低吸收从而提高损伤阈值。由于三种方式处理机制不同,在实际应用中应根据膜层的性能选择合适的处理方式。

不同方法制备的Ta_2O_5薄膜光学性能和激光损伤阈值的对比分析

采用电子束蒸发(EBE)和离子束溅射(IBS)制备了不同的Ta_2O_5薄膜,同时对电子束蒸发制备的薄膜进行了退火处理。研究了制备的Ta_2O_5薄膜的光学性能、激光损伤阈值(LIDT)、吸收、散射、粗糙度、微缺陷密度和杂质含量。结果表明,退火可使电子束蒸发制备的薄膜的光学性能得到改善,接近离子束溅射的薄膜的光学性能。电子束蒸发制备的薄膜的损伤阈值较低的主要原因在于吸收大,微缺陷密度和杂质含量高,而与薄膜的散射和粗糙度关系不大。退火后薄膜的吸收和微缺陷密度都明显降低,损伤阈值得到提高。退火后的薄膜损伤阈值仍然低于溅射得到的薄膜损伤阈值是因为退火并不能降低膜内的杂质含量,因此选用高纯度的蒸发膜料和减少电子束蒸发过程中的污染有可能进一步提高薄膜的损伤阈值。

Investigation of annealing effects on the laser-induced damage threshold of amorphous Ta2O5 films

Ta2O5 films were deposited using the conventional electron beam evaporation method and then annealed at temperatures in the range 373-673 K. Chemical composition, scattering and absorption were examined by X-ray photoelectron spectroscopy (XPS), total integrated scattering (TIS) measurement and the surface thermal lensing (m) technique, respectively. The laser-induced damage threshold (LIDT) was assessed using the output from an Nd:YAG laser with a pulse length of 12 ns. The results showed that the improvement of the LIDT after annealing was due to the reduced substoichiometric and structural defects present in the film. The LIDT increased slightly below 573K and then increased significantly with increase in annealing temperature, which could be attributed to different dominant defects. Moreover, the root mean square (RMS) roughness and scattering had little effect on the LIDT, while the absorption and the LIDT were in accord with a general relation. (c) 2008 Elsevier Ltd. All rights reserved.

Influence of substoichiometer on the laser-induced damage characters of HfO2 thin films

HfO2 is one of the most important high refractive index materials for depositing high power optical mirrors. In this research, HfO2 thin films were prepared by dual-ion beam reactive sputtering method, and the laser-induced damage thresholds (LIDT) of the sample were measured in 1-on-1 mode for laser with 1064 nm wavelength. The results indicate that the LIDT of the as-grown sample is only 3.96 J/cm(2), but it is increased to 8.98 J/cm(2) after annealing under temperature of 200 degrees C in atmosphere. By measuring the laser weak absorption and SIMS of the samples, we deduced that substoichiometer is the main reason for the low LIDT of the as-grown sample, and the experiment results were well explained with the theory of electronic-avalanche ionization. (C) 2008 Elsevier B.V. All rights reserved.

Effects of deposition rates on laser damage threshold of TiO2/SiO2 high reflectors

TiO2 single layers and TiO2/SiO2 high reflectors (HR) are prepared by electron beam evaporation at different TiO2 deposition rates. It is found that the changes of properties of TiO2 films with the increase of rate, such as the increase of refractive index and extinction coefficient and the decrease of physical thickness, lead to the spectrum shift and reflectivity bandwidth broadening of HR together with the increase of absorption and decrease of laser-induced damage threshold. The damages are found of different morphologies: a shallow pit to a seriously delaminated and deep crater, and the different amorphous-to-anatase-to-rutile phase transition processes detected by Raman study. The frequency shift of Raman vibration mode correlates with the strain in. film. Energy dispersive X-ray analysis reveals that impurities and non-stoichiometric defects are two absorption initiations resulting to the laser-induced transformation. (C) 2008 Elsevier B. V. All rights reserved.