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1.
A time-resolved high-power laser photometer, which measures the real-time variations of transmission, internal reflection, and scattering simultaneously with picosecond time resolution, was developed to investigate the material response sequence during high-power nanosecond laser irradiation in thick fused silica. It was found that the transient transmission decreased sharply, accompanied by an increase in internal reflection at the rising edge of the laser pulse. The transient transmission recovered, while laser damage did not occur, but it did not recover if the scattering increased, indicating the occurrence of laser damage. The reason for the sharp decrease of transmission and the relationship between the transmission drop and laser damage were discussed.  相似文献   
2.
Ta2O5/SiO2 dielectric mirrors deposited by ion beam sputtering (IBS) are studied. The multi-shot laserinduced damage threshold (LIDT) and its dependence on the number of shots are investigated, after which we find that the multi-shot LIDT is lower than that of single-shot. The accumulation effects of defects play an important role in the multi-shot laser damage. A simple model, which includes the conduction band electron production vsa multiphoton and impact ionizations, is presented to explain the experimental phenomena.  相似文献   
3.
Based on polarization state conversion, a technique for coaxially coherent combination of laser beams is introduced. Laser beams can be coaxially coupled into one beam with high combination efficiency and perfect beam quality. A polarized laser beam combination system based on master oscillator power amplifier (MOPA) configuration is developed and the efficiencies of both unit combination and the whole system are investigated. In the experiment of combining four beams with single longitudinal mode, a combination efficiency of 85.3% is achieved. It can be further enhanced by improving the stability of experimental environment and the quality of optical and mechanical components.  相似文献   
4.
HfO_2单层膜的吸收和激光损伤阈值测试   总被引:2,自引:0,他引:2       下载免费PDF全文
薄膜吸收是降低膜层激光损伤阈值的重要原因,为了研究薄膜吸收对激光损伤阈值的影响,对HfO2单层膜在1 064 nm处的吸收及其在不同波长激光辐照下的损伤阈值进行了测试和分析。研究结果表明:薄膜的激光损伤阈值由薄膜吸收平均值(决定于薄膜中缺陷的种类和数量)和吸收均匀性(决定于薄膜中缺陷的分布)共同决定;根据HfO2单层膜在1064 nm波长处的吸收值,不但可以定性判断薄膜在1 064 nm波长,而且还可以判断在其它波长激光辐照下的抗激光损伤能力。  相似文献   
5.
基于电子密度演化模型,借助数值方法,研究了飞秒激光作用下光学薄膜内的电子密度演化过程,讨论了初始电子密度Ni和激光脉冲宽度τ对光学薄膜激光损伤阈值Fth的影响,分析了激光诱导薄膜损伤过程中MPI和AI的性质和作用.研究结果表明,对应于一定的脉宽,存在一个临界初始电子密度,当Ni低于这一临界密度时,Fth不受Ni影响;当Ni高于临界密度时,Fth随Ni增加而降低.临界初始电子密度随着脉宽的减小而增加。对于FS和BBS介质薄膜,Fth随脉宽的增加而升高。初始电子密度Ni对BBS中的MPI和AI基本没有影响;同样Ni对FS中的AI基本不产生影响,但当Ni>1011 cm-3时,FS中MPI电子密度随Ni增加而降低.在所研究的脉宽范围τ∈[0.01,5]ps,AI是FS介质激光诱导损伤的主要机制.而对于BBS,当脉宽τ∈[0.03,5]ps,AI是激光诱导损伤的主要机制;当脉宽τ∈[0.01,0.03]ps,MPI在激光诱导损伤中占主导地位.  相似文献   
6.
In the comparison of damage modifications, absorption measurement and energy dispersive x-ray analysis, the effect of vacuum on the laser-induced damage of anti-reflection coatings is analyzed. It is found that vacuum decreases the laser-induced damage threshold of the films. The low laser-induced damage threshold in vacuum environments as opposed to air environments is attributed to water absorption and the formation of the O/Si, O/Zr sub-stoichiometry in the course of laser irradiation.  相似文献   
7.
 为了研究高功率系统中高反膜的损伤机制,对高功率系统中最常用的基频高反膜进行了损伤实验。利用台阶仪、扫描电镜、表面轮廓仪等手段,对实验样品的典型损伤形貌进行了比较和分析。结果表明:保护膜的存在增强了样品的抗激光损伤能力;未加保护膜样品的典型破坏形貌是由材料热物特性差异导致的分层剥落损伤,这类损伤在后续的脉冲辐照下会迅速发展;有保护膜样品的典型破坏形貌是中心带有μm量级小坑的等离子体烧蚀损伤区,其主要是由缺陷受热力作用喷溅导致,小坑附近膜面的凸起是这种力学作用的宏观体现,这类损伤在后续的脉冲辐照中表现得相对比较稳定。保护膜的存在,在一定程度上抑制了分层剥落这种灾难性损伤的出现,改善了样品的损伤特性。  相似文献   
8.
抑制损伤发展的CO_2激光修复技术及机理研究   总被引:1,自引:1,他引:0  
熔石英表面激光损伤发展问题一直制约着激光器的运行通量。采用CO2激光在线熔融修复损伤点,修复后形成一个光滑的高斯坑,去除了损伤点中的裂纹,平滑了凹凸不平的表面,并且在紫外脉冲激光作用下,修复斑再次产生损伤的阈值高于熔石英元件的损伤生长阈值。因此CO2熔融修复技术能有效地抑制损伤发展。通过分析CO2激光作用下熔石英表面的温度分布,讨论修复坑的形成过程,确定激光参数对修复效果的影响,为寻找最佳修复参数提供理论基础。同时利用原子力显微镜(AFM)、轮廓仪细致分析损伤点和修复斑的微细结构,采用有限差分时域方法计算损伤点和修复斑周围的光强分布,探索消除裂纹和平滑表面对抑制损伤生长的作用。  相似文献   
9.
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.  相似文献   
10.
 采用计算模拟的方法,研究了光栅式扫描预处理的扫描方式以及脉冲能量波动、定位误差对预处理效率的影响。研究发现,脉冲能量波动及其定位误差使预处理效率降低,同时其影响与扫描方式之间存在相互调制作用,因此可以通过选择合适的扫描方式以及扫描间隔来优化预处理流程,提高预处理效率。此外发现,光斑呈等边三角形排列时的预处理效率优于正方形。  相似文献   
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