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《物理学报》2016,(15)
对1064 nm纳秒激光辐照下熔石英元件后表面损伤过程进行了时间分辨诊断.利用基于偏振原理的单发双帧阴影成像系统捕捉了脉冲上升沿开始到数百纳秒尺度内的瞬态材料响应,并结合剪切干涉成像系统分析了空气端等离子体微喷现象.结果表明,损伤在脉冲上升沿就己经发生,此时空气端等离子体的膨胀速度高达20 km/s,同时材料内部也存在高速扩张的不透明损伤区域,但其扩张过程在脉冲结束后迅速停止;损伤发生后数十纳秒后,空气端出现大量中性物质喷发基于激光支持的固态吸收波前模型与相爆炸理论对这些现象进行了讨论.对空气端等离子体扩张过程进行了数值模拟,结果表明空气端等离子体压强、温度与密度等参数值随延迟增加迅速下降,其瞬态压强最高达600 MPa;模拟结果还预测了向内扩张的内激波的形成.研究结果对理解熔石英元件的损伤机理有重要意义. 相似文献
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光学元件激光损伤是限制高功率激光装置输出能力的关键因素,为了理解光学元件激光损伤过程,提高光学元件抗激光损伤性能,利用偏振阴影显微镜成像技术和光电探测技术研究了紫外皮秒激光诱使熔石英光学元件损伤的时间分辨动力学过程。结果显示了紫外皮秒激光作用过程中冲击应力波的传输特性、瞬态吸收的演变过程以及裂缝的发展过程。结果表明,冲击应力波的传输速度约为6.9μm/ns;532nm波长的激光瞬态吸收在激光作用之后2.5μs时激光吸收达到最大值,之后缓慢下降,整个持续时间可达50μs以上;损伤裂纹在7.5ns时刻就基本停止增长。研究结果对理解皮秒激光的损伤机制有重要意义。 相似文献
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利用光学元件激光损伤测试平台,测试了355 nm皮秒激光辐照下熔石英光学元件的初始损伤及损伤增长情况,并通过荧光检测分析了损伤区缺陷。研究结果表明:皮秒激光较高的峰值功率导致熔石英损伤阈值较低,前表面损伤阈值为3.98 J/cm2,后表面损伤阈值为2.91 J/cm2;前后表面损伤形貌存在较大差异,后表面比前表面损伤程度轻且伴随体内丝状损伤;随脉冲数的增加后表面损伤直径增长缓慢,损伤深度呈线性增长;皮秒激光的动态自聚焦和自散焦导致熔石英体内损伤存在细丝和炸裂点重复的现象;与纳秒激光损伤相比,损伤区缺陷发生明显改变。 相似文献
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利用光学元件激光损伤测试平台,测试了355 nm皮秒激光辐照下熔石英光学元件的初始损伤及损伤增长情况,并通过荧光检测分析了损伤区缺陷。研究结果表明:皮秒激光较高的峰值功率导致熔石英损伤阈值较低,前表面损伤阈值为3.98 J/cm2,后表面损伤阈值为2.91 J/cm2;前后表面损伤形貌存在较大差异,后表面比前表面损伤程度轻且伴随体内丝状损伤;随脉冲数的增加后表面损伤直径增长缓慢,损伤深度呈线性增长;皮秒激光的动态自聚焦和自散焦导致熔石英体内损伤存在细丝和炸裂点重复的现象;与纳秒激光损伤相比,损伤区缺陷发生明显改变。 相似文献
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研究了熔石英玻璃元件在纳秒激光等离子体冲击波作用下的表面和横截面损伤形貌,利用有限元法模拟了冲击波在熔石英玻璃内部的传播规律,并基于冲击波在玻璃内部的应力分布规律分析了损伤形成机理.研究发现:在冲击波作用下,石英玻璃会受到沿波面方向的压应力和沿波面切方向的拉应力,在这两种力的作用下,造成以激光辐照中心的弧状层状断裂和沿径向的断裂;冲击波的反射叠加还会使局部拉应力增大,造成靠近后表面的损伤.有限元法能够直观地分析等离子体冲击波对光学元件的作用,并分析光学元件在等离子体冲击波下的损伤机理. 相似文献
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发展了355 nm纳秒激光下亚波长杂质粒子引起熔石英损伤的基本模型。通过Mie散射理论和热传导方程,计算了粒子与熔石英边界处的温度随粒子尺寸的变化关系,并分析了达到临界温度时,不同粒子诱导损伤所需的关键能量密度,讨论了各粒子最易引起熔石英损伤的尺寸。实验采用355 nm纳秒激光脉冲作用熔石英及其HF刻蚀样品,测得两者的损伤概率。研究表明:粒子吸收激光能量,随着粒子半径的增加,其边缘温度先增大后减小,一定尺寸范围内的粒子才会引起熔石英的损伤;关键能量密度所对应的粒子半径为最易引起熔石英损伤的关键粒子半径;经刻蚀后,熔石英样品表面杂质数密度降低,损伤概率降低,损伤阈值提高。 相似文献
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采用感应耦合等离子体刻蚀技术,以CF4/Ar/O2为反应气体对熔石英元件表面进行修饰,研究并分析了CF4和Ar流量对刻蚀速率、熔石英表面粗糙度和微观形貌的影响。结果表明,CF4化学刻蚀与Ar的物理轰击对熔石英样品表面修饰效果存在一定竞争关系,当它们达到平衡时表面粗糙度最小。通过对不同流量气体刻蚀过后熔石英表面粗糙度和光学显微形貌分析获得了较为理想的气流量配比,该研究为反应等离子体修饰熔石英光学元件以获得较高光学性能提供工艺参考。 相似文献
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在熔石英表面人工溅射一层Al膜污染物,分别测试污染前后熔石英基片在355 nm波长激光辐照下的损伤阈值,并采用透射式光热透镜技术、椭偏仪和光学显微镜研究了污染物Al膜的热吸收、厚度以及激光辐照前后熔石英的损伤形貌。用355 nm波长的脉冲激光分别辐照位于污染的熔石英和洁净的熔石英前后表面的损伤点,并用显微镜在线采集损伤增长图样,测试损伤点面积。实验表明:熔石英前表面的金属Al膜污染物导致基片损伤阈值的下降约30%,后表面的污染物导致基片下降约15%,位于熔石英样片后表面损伤点面积随激光辐照次数呈指数增长,而位于前表面的损伤点面积与激光脉冲辐照次数呈线性增长关系;带有污染的熔石英样片的增长因子比洁净的熔石英样片的增长因子高30%。 相似文献
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In order to understand the physical mechanism, time-resolved dynamics of 355 nm nanosecond laser induced entrance and exit surface damage on fused silica was investigated by using shadow graphic technique. The results show that the damage mechanism is different between the entrance and exit surface during nanosecond laser interaction with fused silica. The plasma and shock waves in air is relatively higher at the entrance surface. The entrance surface damage is reduced because plasma shielding limits energy deposition. Without plasma shielding, the exit surface damage is more serious for more laser energy deposition in material. And without the stress of plasma and shock waves, the material is ejected easily at rear surface. These are confirmed by damage micrograph at the entrance and exit surface. 相似文献
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Two sets of laser-damage experiments on large-aperture fused silica optics have been carried out in a high-power laser facility. Severe damage has been found on the grating which presented dense craters on the front surface. This phenomenon is quite different from other fused silica optics, which are damaged on the rear surface. The damage possibility due to the redeposition layer was ruled out by acid-etching the grating’s front surface. The remarkable stimulated Brillouin scattering (SBS) effect was observed in grating and the reason for the front surface damage is thought to be the backward SBS. 相似文献
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《中国物理 B》2019,(8)
The damage to the rear surface of fused silica under the action of high power laser is more severe than that incurred by the front surface, which hinders the improvement in the energy of the high power laser device. For optical components,the ionization breakdown by laser is a main factor causing damage, particularly with laser plasma shock waves, which can cause large-scale fracture damage in fused silica. In this study, the damage morphology is experimentally investigated, and the characteristics of the damage point are obtained. In the theoretical study, the coupling and transmission of the shock wave in glass are investigated based on the finite element method. Thus, both the magnitude and the orientation of stress are obtained. The damage mechanism of the glass can be explained based on the fracture characteristics of glass under different stresses and also on the variation of the damage zone's Raman spectrum. In addition, the influence of the glass thickness on the damage morphology is investigated. The results obtained in this study can be used as a reference in understanding the characteristics and mechanism of damage characteristics induced by laser plasma shock waves. 相似文献
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Numerical simulation of the modulation to incident laser by the repaired damage site in a fused silica subsurface
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One of the main factors of laser induced damage is the modulation to incident laser which is caused by the defect in the subsurface of the fused silica.In this work,the repaired damage site irradiated by CO 2 laser is simplified to a Gaussian rotation according to the corresponding experimental results.Then,the three-dimensional finite-difference time-domain method is employed to simulate the electric field intensity distribution in the vicinity of this kind of defect in fused silica front subsurface.The simulated results show that the modulation is notable,the E max is about 2.6 times the irradiated electric field intensity in the fused silica with the damage site (the width is 1.5 μm and depth is 2.3 μm) though the damage site is repaired by CO 2 laser.The phenomenon and the theoretical result of the annular laser enhancement existed on the rear surface are first verified effectively,which agrees well with the corresponding experimental results.The relations between the maximal electric field intensity in fused silica with defect depth and width are given respectively.Meanwhile,the corresponding physical mechanism is analysed theoretically in detail. 相似文献
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采用ANSYS进行形变-应力模拟。对不同应力状态下的熔石英表面进行三倍频激光损伤测试,结果发现,预加压应力为0~50 MPa时损伤阈值有明显提高的趋势,用应力耦合作用对此给出了解释:0~50 MPa的预加压应力可以降低和抵消激光辐照产生的张应力破坏,大于50 MPa预应力的耦合作用会使得该处机械性能下降,另外,损伤增长在预应力存在时更容易发生。因此,0~50 MPa预加压应力时的表面预应力可以提高熔石英的抗激光辐照能力。 相似文献
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采用3维时域有限差分方法和完全匹配吸收层,模拟了长方体缺陷在熔石英前后表面时对入射激光为TM波的调制作用,绘出了截面上的电场强度分布及最大电场强度随熔石英深度变化的曲线,并进行了比较和分析。结果表明:缺陷在前表面上时,后表面附近的最大电场强度2.522 41 V/m大于缺陷附近的1958 83 V/m;缺陷在后表面上时,材料中的最大电场强度为2.799 38 V/m,且出现在后表面附近。无论该缺陷在前表面还是在后表面,最大电场强度都是出现在后表面附近,表明光学材料的后表面在一定程度上更容易被损伤。 相似文献
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采用3维时域有限差分方法和完全匹配吸收层,模拟了长方体缺陷在熔石英前后表面时对入射激光为TM波的调制作用,绘出了截面上的电场强度分布及最大电场强度随熔石英深度变化的曲线,并进行了比较和分析。结果表明:缺陷在前表面上时,后表面附近的最大电场强度2.522 41 V/m大于缺陷附近的1958 83 V/m;缺陷在后表面上时,材料中的最大电场强度为2.799 38 V/m,且出现在后表面附近。无论该缺陷在前表面还是在后表面,最大电场强度都是出现在后表面附近,表明光学材料的后表面在一定程度上更容易被损伤。 相似文献
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为了提高熔石英元件表面抗激光损伤阈值,利用超声波辅助HF酸研究平滑光学元件表面缺陷形貌和去除刻蚀后残留物效果,通过扫描电子显微镜电镜和原子力显微镜记录表面形貌结构,以及单脉冲激光辐照测试抗损伤阈值确定实验参数。研究表明,超声波场的引入能催化HF酸的刻蚀速率、提高钝化效果并且更易剥离嵌入的亚μm级杂质粒子。经过实验测试,获得了熔石英类元件相匹配的超声辅助HF酸刻蚀实验参数,研究结果对应用超声波辅助HF酸研究熔石英表面抗激光损伤有重要意义。 相似文献