液晶光学器件功能薄膜的激光损伤机理研究

Laser Damage on Functional Films of Liquid Crystal Optical Elements

作者: 专业:光学 导师:王伟平 年度:2010 学位:硕士  院校: 中国工程物理研究院

Keywords

Laser irradiation, Liquid Crystal Optical Elements, Indium tin oxide films, Polyimide films, Laser damage

        液晶光学器件在光束整形、激光偏振态和相位控制等激光束精密控制技术上具有重要的应用潜力,但其能否在强激光系统中应用,其中一个重要指标是其抗激光损伤能力。本论文研究了连续波及脉冲体制(脉宽为10 ns)近红外激光(波长为1064 nm)对液晶光学器件功能膜层材料的损伤阈值和机理。建立了各膜层材料激光热损伤的物理模型,并进行了相关实验和数值模拟研究。建立了激光辐照氧化铟锡(ITO)导电薄膜的温度场和热应力计算模型,计算结果表明:1064 nm激光对ITO薄膜的损伤主要为热应力损伤;连续波激光辐照下,薄膜损伤始于薄膜与基底之间的界面处附近;脉冲激光辐照下,由于作用时间短,温升主要发生在光斑范围内的膜层,薄膜从表面开始损伤。实验研究了ITO的光电性能,测试了薄膜的吸收光谱曲线及方块电阻;利用泵浦-探测技术研究了其激光损伤现象,使用1-on-1法测定了氧化铟锡薄膜的50%损伤几率阈值;研究了不同功率密度激光辐照后薄膜方块电阻的变化。实验结果表明:薄膜越厚,方块电阻越小,激光损伤阈值越低;薄膜未完全损伤前,方块电阻随激光功率密度的增大而增大。研究了激光与PI薄膜材料的耦合机制及近红外激光辐照对PI薄膜的损伤,其损伤机理主要是激光加热导致其热分解。实验结果表明PI薄膜对1064 nm脉冲激光100%损伤几率阈值为25 J/cm2。建立了激光辐照PI薄膜的热计算模型,考虑了材料的分解放热。脉冲激光辐照PI薄膜(K9玻璃基底)的计算结果与实验结果相符合。计算了连续激光辐照50μm厚PI薄膜(无基底)的温度场,表明其对连续激光损伤阈值较高。实验研究了液晶材料的激光损伤,其机理主要是激光加热导致其温度超过清亮点温度(65℃)时,液晶材料从各向异性变为各向同性,液晶器件功能暂时失效;温度超过300℃后,液晶材料发生气化、分解以至碳化导致液晶器件的永久失效。实验结果表明:1064 nm、10ns激光脉冲作用时,液晶材料永久损伤的阈值为20J/cm2,略低于理论计算值,主要是因为计算中未考虑液晶盒中局部杂质、激光光强分布不均等因素的影响。建立了含有K9玻璃、ITO导电膜、PI取向膜和液晶材料的整体液晶光学器件的激光热损伤计算模型,给出了激光辐照后各部分的温度分布。分析了激光辐照下各膜层对液晶光学器件的影响,ITO薄膜和PI薄膜对1064 nm波长激光的吸收系数很大,导致激光沉积引起温升较大,是引起激光损伤的主要原因。
    The liquid crystal optical elements have important potential applications on laser beams precision controlling technology (including laser beams shaping, laser polarization state controlling, laser phase modulation, et al.). Laser damage threshold is one of the most important parameters when considering liquid crystal optical elements used in high intensity laser system. Laser damage of the films in liquid crystal optical elements were investigated using CW and pulsed 1064 nm laser in this paper. The damage threshold and damage mechanism of the films were obtained by experiments and simulations.The temperature and stress distributions of indium tin oxide (ITO) films after laser irradiation were simulated. The absorption spectrum and square resistance of ITO were tested. The laser damage on ITO films was studied through pump-probe technology, 50% damage probabilities threshold of ITO were obtained by 1-on-1 testing and square resistance of the films after laser irradiation is measured. The results indicate that the ITO films are damaged due to laser induced thermal stress, and the laser damage threshold decrease with the increase of thickness of ITO films. The damage begins near the interface of ITO film and K9 glass after continuous wave laser irradiation, while the damage begins on the surface of ITO film after pulsed laser irradiation.The coupling and damage mechanisms of near infrared laser interaction with polyimide (PI) films were studied. The laser heats up the films leading to thermal decomposition.100% damage probabilities threshold of PI using pulsed laser (1064 nm,10 ns) is about 25 J/cm2 The thermal-physical mode of laser irradiation on PI was established, considering the exothermic reaction of thermal decomposition. The simulated results of pulsed laser irradiation on PI films basically agree with the experimental data. The temperature distribution of PI films (50μm) after continuous wave laser irradiation is simulated, the result indicates that the laser damage threshold is large.The laser damage on liquid crystal materials (LC) was studied in experiments, 100% damage probabilities threshold of LC materials is about 20 J/cm2. The damage mechanism is that the laser heats up the LC materials, and the electro-optical anisotropy of LC materials turn to electro-optical isotropy when the temperature of LC materials is higher than 65℃, leading to the liquid crystal optical elements fail temporarily. The LC materials decompose and carbonize when the temperature of LC materials is higher than 300℃, leading to the liquid crystal optical elements fail forever. The experimental result indicates that the damage threshold of LC materials is 20 J/cm2 after near infrared laser (1064 nm, 10 ns) irradiation.The calculating model of laser damage on liquid crystal optical elements (including ITO, PI, LC and K9 glass) was established, and the temperature distribution in the liquid crystal optical elements after near infrared laser irradiation was simulated. The large laser absorption coefficients of ITO and PI are the main reason of laser damage.
        

液晶光学器件功能薄膜的激光损伤机理研究

摘要4-6
ABSTRACT6-7
第1章 引言10-18
    1.1 液晶光学器件在光束精密控制中的应用10-11
    1.2 本论文研究的目的和意义11-12
    1.3 国内外研究现状12-16
        1.3.1 激光与聚合物相互作用应用研究进展12-13
        1.3.2 激光与聚合物相互作用理论研究进展13-14
        1.3.3 激光与聚合物相互作用实验研究进展14-15
        1.3.4 激光与ITO相互作用研究进展15-16
    1.4 论文的主要工作16-18
第2章 激光与ITO薄膜相互作用研究18-38
    2.1 ITO的电学性能18-22
        2.1.1 ITO薄膜的半导体特性18-19
        2.1.2 薄膜方块电阻定义及测量19-21
        2.1.3 ITO薄膜厚度对电阻率的影响21-22
    2.2 ITO的光学性能22-25
        2.2.1 ITO薄膜透射区范围22-23
        2.2.2 ITO薄膜的透射、反射和吸收光谱的测量23-25
    2.3 激光辐照ITO透明导电薄膜的实验研究25-28
        2.3.1 激光辐照对ITO薄膜方块电阻影响26-27
        2.3.2 激光辐照ITO薄膜的形貌分析27-28
    2.4 激光辐照ITO透明导电薄膜的理论计算28-36
        2.4.1 计算模型28-30
        2.4.2 计算结果分析30-35
        2.4.3 计算结果与实验结果比较35-36
    2.5 激光辐照对ITO薄膜的影响36
    2.6 小结36-38
第3章 激光辐照聚酰亚胺薄膜的研究38-48
    3.1 聚酰亚胺简介38-39
    3.2 聚酰亚胺的热分析39-40
    3.3 激光与聚酰亚胺的耦合机制40-41
    3.4 激光辐照聚酰亚胺材料的实验研究41-42
    3.5 激光与聚酰亚胺材料相互作用理论计算42-45
        3.5.1 激光与聚酰亚胺材料相互作用理论计算42-43
        3.5.2 激光与玻璃基底聚酰亚胺薄膜相互作用理论计算43-45
    3.6 激光辐照对PI薄膜的影响45-46
    3.7 小结46-48
第4章 激光与液晶光学器件相互作用研究48-58
    4.1 液晶材料的激光损伤实验研究48-50
    4.2 激光辐照液晶的理论计算50-51
    4.3 激光辐照液晶光学器件的理论计算51-55
    4.4 激光辐照下各膜层对液晶光学器件的影响55
    4.5 小结55-58
第5章 总结与展望58-60
    5.1 本论文主要工作得出结论58-59
    5.2 论文研究工作的展望59-60
参考文献60-65
致谢65-66
攻读硕士学位期间发表的论文66
        下载全文需10


本文地址:

上一篇:地籍数据归户管理相关技术研究及其应用
下一篇:电晕稳定开关的研究

分享到: 分享液晶光学器件功能薄膜的激光损伤机理研究到腾讯微博           收藏
评论排行
公告