Development of high-power OPCPA laser at 1064 and 780 nm

A compact 10-TW/100-fs level ultrashort-pulse and ultra-intense laser system at 1064 nm based on optical parametric chirped pulse amplification (OPCPA) scheme is described, at which the pump and seed for the optical parametric amplification (OPA) process is optically synchronized. We investigated the output stability and the conversion efficiency of the system. Moreover, a design toward higher peak power output is given and an optically synchronized amplifier based on the concept of OPCPA at 800 nm is preliminarily explored.

Laser-induced damage of Ta2O5/S1O2 narrow-band interference filters under different 1064 nm Nd : YAG laser modes

The laser-induced damage (LID) behavior of narrow-band interference filters was investigated with a Nd:YAG laser at 1064 nm under single-pulse mode and free-running mode. The absorption measurement of such coatings was performed with surface thermal lensing (STL) technique. The damage morphologies under the two different laser modes were also studied in detail. It was found that all the filters exhibited a pass-band-center-dependent absorption and laser-induced damage threshold (LIDT) behavior, but the damage morphologies were diverse. The explanation was given with the analysis of the electric field distribution and the operational behavior of the irradiation laser. (c) 2005 Elsevier B.V. All rights reserved.

Ta2O5膜在532, 800 和 1064 nm波长的n-on-1体系下的激光损伤阈值研究

Ta2O5膜采用传统的电子束蒸发方法制备，并在氧气中673 K的条件下进行了退火12 h处理。首先在1-on-1体系下对Ta2O5膜进行了532和1064 nm波长下的激光损伤阈值（LIDT） 研究，然后在n-on-1体系下分别对532，800和1064 nm三种波长下的激光损伤阈值进行了研究。结果表明在n-on-1体系下Ta2O5膜在532和1064 nm波长下的阈值均高于1-on-1体系下的阈值。此外，在n-on-1体系下，薄膜的阈值随波长增加而增大。同时发现，在氧气中进行退火对Ta2O5膜的光学性能

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 (AR) coatings at 1064 nm made by Ta2O5/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 24.5 J/cm(2) in air to 15.7 J/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.

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。

三硼酸锂晶体上1064 nm, 532 nm, 355 nm三倍频增透膜的设计

采用矢量法设计了三硼酸锂晶体上1064 nm、532 nm和355 nm三倍频增透膜,结果表明1064 nm、532 nm和355 nm波长的剩余反射率分别为0.0017％、0.0002％和0.0013％。根据误差分析,薄膜制备时沉积速率精度控制在＋5.5％时,1064 nm、532 nm和355 nm波长的剩余反射率分别增加至0.20％、0.84％和1.89％。当材料折射率的变化控制在＋3％时,1064 nm处的剩余反射率增大为0.20％,532 nm和355 nm处分别达0.88％和0.24％。与薄膜

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，

Laser-induced damage of Ti O2 Si O2 high reflector at 1064 nm

A high laser-induced damage threshold (LIDT) TiO2/SiO2 high reflector (HR) at 1064 nm is deposited by e-beam evaporation. The HR is characterized by optical properties, surface, and cross section structure. LIDT is tested at 1064 nm with a 12 ns laser pulse in the one-on-one mode. Raman technique and scanning electron Microscope are used to analyze the laser-induced modification of HR. The possible damage mechanism is discussed. It is found that the LIDT of HR is influenced by the nanometer precursor in the surface, the intrinsic absorption of film material, the compactness of the cross section and surface structure, and the homogeneity of TiO2 layer. Three typical damage morphologies such as flat-bottom pit, delamination, and plasma scald determine well the nanometer defect initiation mechanism. The laser-induced crystallization consists well with the thermal damage nature of HR. (C) 2008 American Institute of Physics.

Influence of different substrates on laser induced damage thresholds at 1064 nm of Ta2O5 films

Ta2O5 films are prepared on Si, BK7, fused silica, antireflection (AR) and high reflector (HR) substrates by electron beam evaporation method, respectively. Both the optical property and laser induced damage thresholds (LIDTs) at 1064 nm of Ta2O5 films on different substrates are investigated before and after annealing at 673 K for 12h. It is shown that annealing increases the refractive index and decreases the extinction index, and improves the O/Ta ratio of the Ta2O5 films from 2.42 to 2.50. Moreover, the results show that the LIDTs of the Ta2O5 films are mainly correlated with three parameters: substrate property, substoichiometry defect in the films and impurity defect at the interface between the substrate and the films. Details of the laser induced damage models in different cases are discussed.

Laser induced damage threshold at 355 and 1064 nm of Ta2O5 films of different phases

Ta2O5 films are deposited on fused silica substrates by conventional electron beam evaporation method. By annealing at different temperatures, Ta2O5 films of amorphous, hexagonal and orthorhombic phases are obtained and confirmed by x-ray diffractometer ( XRD) results. X-ray photoelectron spectroscopy ( XPS) analysis shows that chemical composition of all the films is stoichiometry. It is found that the amorphous Ta2O5 film achieves the highest laser induced damage threshold ( LIDT) either at 355 or 1064 nm, followed by hexagonal phase and finally orthorhombic phase. The damage morphologies at 355 and 1064 nm are different as the former shows a uniform fused area while the latter is centred on one or more defect points, which is induced by different damage mechanisms. The decrease of the LIDT at 1064nm is attributed to the increasing structural defect, while at 355nm is due to the combination effect of the increasing structural defect and decreasing band gap energy.

Further analysis of indentation loading curves: Effects of tip rounding on mechanical property measurements

The effects of indenter tip rounding on the shape of indentation loading curves have been analyzed using dimensional and finite element analysis for conical indentation in elastic-perfectly plastic solids. A method for obtaining mechanical properties from indentation loading curves is then proposed. The validity of this method is examined using finite element analysis. Finally, the method is used to determine the yield strength of several materials for which the indentation loading curves are available in the literature.