共查询到18条相似文献,搜索用时 312 毫秒
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实验研究并分析了调Q Nd:YAG 脉冲激光诱导光纤损伤特性.设计了在真空条件下全石英光纤传输1064 nm 脉冲激光实验.通过将激光注入光纤端面气压降低到10—100 Pa, 光纤端面击穿阈值提高到大气环境下的185 倍.结合光纤端面损伤形貌分析可知,光纤端面损伤主要是由于激光驻波场和烧蚀共同作用的结果,光纤端面或内部大量的缺陷降低了光纤抗激光损伤的能力.在真空条件下由于光纤端面光学击穿阈值的提高,激光诱导光纤损伤特性又表现出了另外一种损伤模式——光纤初始输入段损伤.它发生在光纤输入段附
关键词:
激光损伤
光束传输
真空
石英光纤 相似文献
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脉冲激光诱导光纤损伤的测试方法 总被引:3,自引:0,他引:3
针对传能光纤的高峰值功率激光损伤过程,研究了光纤损伤测试方法。实验装置搭建中增加了定位孔,有利于激光注入光纤对准;分别采用刀口法和CCD法对入射光束不同截面处光斑大小进行了测量,两种方法的测量结果基本一致。参考GJB1487-92激光光学元件测试方法和ISO11245光学表面的激光诱导损伤阈值测试方法,采用N-ON-1损伤测试和有效光斑面积计算方法对芯径为400 μm的石英包层阶跃折射率石英光纤进行了损伤阈值测试。实验发现:光纤损伤部位全部为入射端面,利用200倍显微镜观察光纤端面,出现明显永久性损伤点。最后采用统计学原理和线性拟合等方法得出测试光纤的端面零概率损伤阈值为3.85 GW/cm2。 相似文献
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实验研究了石英光纤的纳秒激光诱导损伤行为.实验条件下全部为光纤端面损伤,按照损伤形貌可以分为坑状损伤、熔融损伤和溅射损伤三类.提出了光纤端面损伤的判断方法和损伤阈值的测试方法,通过线性拟合得出实验条件下石英传能光纤的零概率损伤功率密度阈值为3.85GW/cm2.总结了光纤端面损伤的过程,分析了激光诱导光纤端面损伤机理,指出光纤端面的杂质缺陷是造成光纤抗激光损伤能力下降的内因.因此,通过改善光纤端面质量还可较大程度提高光纤传输激光能量.实验发现光纤注入端面损伤点几乎全部发生在端面中心区
关键词:
激光诱导损伤
高峰值功率
光纤传能
损伤阈值 相似文献
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通过激光放大器获得高功率的激光输出时,增益材料的损伤特性决定了激光器的使用寿命。以激光二极管(LD)端面泵浦的单片钕玻璃激光放大器为例,对泵浦过程增益材料内部的光场特性和热效应引起的端面应变进行了研究。结合电子增殖理论,建立了一个激光增益材料场致损伤特性分析模型。研究了增益材料内部的雪崩电离速率和多光子电离速率的变化规律,并根据临界自由电子数密度确定了材料发生损伤的具体位置。研究结果表明,激光增益材料发生损伤的位置受到信号光初始光强值、脉冲宽度和泵浦光功率密度影响。当初始光场能量一定,脉冲宽度从10 ns增加到13 ns时,损伤点向入射端方向移动大约14 mm。泵浦光功率密度越大,端面热效应越明显,材料更容易发生损伤。 相似文献
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构建了一种基于光纤传输高功率激光的飞片发射系统,并测试了飞片速度.飞片膜层为三明治结构:铝烧蚀层、氧化铝隔离层和铝飞片产生层.飞片膜层采用磁控溅射技术沉积在玻璃衬底上,总厚度为5.5 μm.激光辐照铝膜层产生高温高压等离子体,驱动剩余膜层产生高速飞片,速度达数km/s.同时,实验研究了光纤传能系统的输出激光空间分布特性和传输激光能量容量,它们决定了飞片的平面性和最大速度.光纤端面损伤是限制光纤传输激光能量容量的关键因素,光纤端面通过精密机械抛光和激光预处理可以获得理想的抗激光损伤能力.采用基于光纤阵列探针的时间序列测试技术获得了飞片的平均速度,并评估了飞片的平面性.采用搭建的基于光纤传输高功率激光的飞片发射系统获得了速度达1.7 km/s、直径接近1 mm的高速飞片.
关键词:
激光驱动飞片
激光辐照
光纤阵列探针
激光等离子体 相似文献
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三种不同端面光纤列阵和半导体激光列阵耦合的(数值)模拟 总被引:2,自引:0,他引:2
半导体激光列阵的输出光束有较大的发散角和较强的不对称性,极大地限制了其在各领域中的应用。为了改善半导体激光列阵输出光束的质量,必须采用特殊的光学系统进行光束整形。一种简单有效的方法是利用光纤列阵实现光束由线性排列到圆形排列的转换。对三种特殊制备的光纤列阵和半导体激光列阵的耦合特性进行了数值模拟研究。结果显示,相对于球形端面光纤列阵和锥形端面光纤列阵,球顶锥形端面光纤列阵和半导体激光列阵有着更高的耦合效率(90%以上)。此外,利用球顶锥形端面光纤列阵还可以进一步压缩输出光束的发散角,从而获得更高质量的输出光束。 相似文献
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激光注入误差对多模光纤传能特性影响分析 总被引:2,自引:0,他引:2
采用ZEMAX软件对激光光纤注入系统进行了建模,仿真分析了激光注入光纤横向偏移、角度偏移对光纤传输激光能量特性的影响.结果表明,光纤输出激光能量分布与激光注入对准误差密切相关.注入误差引起光纤初始输入段激光峰值功率密度的剧烈波动,出现了一个激光峰值功率密度极大值,这个极大值是可以达到光纤截面内激光平均功率密度的数十倍;横向偏移激发大量斜光线产生,使光纤输出激光能量分布匀化;角度偏移仅影响光纤内子午光线与斜光线的传播方向,对光纤内激光能量分布的匀化作用较弱. 相似文献
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本文针对惯性约束聚变驱动器终端光学系统中连续相位板置于基频光路(前置)时,频率转换晶体内部光场分布进行了研究.经研究发现连续相位板前置对基频光的相位调制降低了频率转换效率,增大了频率转换晶体内部光场的不均匀性,它导致晶体激光诱导损伤风险的可能性加大.值得特别注意的是:在频率转换晶体入射和出射端面附近激光调制度和最大光强相对于其他区域高,发生激光诱导损伤的可能性相对更大.因此当不断增大频率转换系统输入的基频光光强时,为保证惯性约束聚变终端光学系统的正常运行需要把连续相位板前置对频率转换晶体内部光场分布的影响
关键词:
惯性约束聚变
连续相位板
频率转换晶体
激光诱导损伤 相似文献
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M. O. Kaptakov V. I. Revenko M. E. Kustov I. S. Kurchatov V. V. Skroznikova T. B. Kiseleva V. V. Buchanov E. N. Murav’ev M. A. Kazaryan E. A. Kuznetsova E. F. Solinov V. I. Skachkov 《Bulletin of the Lebedev Physics Institute》2018,45(9):272-278
Some principal aspects of silicate glass cutting by controlled laser through thermal cleavage are considered. In particular, it is shown that the cutting speed in the case of ytterbium fiber laser radiation with a wavelength of 1.065 μm lying in fact in the glass transmission range (more precisely, in the low absorption region) depends linearly on the laser power. It is shown that the glass end face takes various geometrical shapes under various conditions of bulk heating and cooling. Therefore, to obtain a homogeneous end face, it is required to stabilize both the laser radiation power and the laser beam speed at a corresponding laser beam geometry in the cut region. Methods for obtaining various cross section shapes of the glass end face and methods for obtaining blunt edges of end faces are presented. 相似文献
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传统的沿z轴光纤传输光线的轨道角动量(orbital angular momentum,OAM)光束的制备方法共同之处都是从内部结构着想,光束的主光线基本上不变,只是波面在变.但要获得携带高mh的光有一定的难度.针对上述问题,本文建立以波面不变,光束主光线变化为基础的理论框架,利用微分几何理论验证不沿z轴圆柱型光纤螺线圈传输的光线可以携带高mh OAM的理论设想.研究发现:利用流动坐标(α,β,γ)计算光线在绕圆柱体的光纤中传输时光纤截面的衍射分布图呈现涡旋特征,有高阶OAM模式.当θ=θ0时,圆柱形轨道光纤过渡到直线轨道光纤.计算光线沿直线传输时光纤截面的衍射分布图是Airy斑,即圆孔衍射斑,无高阶OAM模式. 相似文献
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A retarding structure that allows the effective admittance of a tube wall to increase smoothly along the tube axis is considered. The sound velocity gradually decreases along a finite segment of the tube and finally vanishes at some cross section. The time of the sound propagation along this segment is infinitely long. A wave incident on the input cross section cannot reach the other end of the tube within a finite time, and, hence, it is not reflected from it. The wave is completely absorbed, the absorption being caused by the energy accumulation in the cross section where the velocity of sound vanishes, rather than by the energy transformation to heat, as in common sound absorbers. A differential equation is obtained to describe the sound propagation in a one-dimensional waveguide with a varying cross section and varying acoustic admittance of the walls. The solutions to this equation are analyzed in the WKB approximation. An exact solution is determined for the case of some specific functions describing the variations of the cross section and admittance. Calculated results for the input admittance of the waveguide are presented. A possible similarity to the problem of shear waves in sea sediments is pointed out. 相似文献
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以粘红酵母菌Rhodotorula glutinis AY 91015为材料, 研究了不同传能线密度(LET)的C离子对粘红酵母菌的失活截面和突变截面, 评估了不同LET的C离子对微生物的失活效应和突变效应。 结果表明, C离子LET为120.0 keV/μm时, 单个粒子对粘红酵母菌的失活截面最大, 为4.37 μm2, 接近酵母菌细胞核的平均核截面; LET为96.0 keV/μm时, 单个粒子对粘红酵母菌的突变截面最大。 通过对C离子束致突变能力的分析发现, C离子在LET为58.2 keV/μm时突变能力最强, 这一结果显示在经C离子辐照后存活下来的粘红酵母菌中, 可以引起有效突变的最佳LET为58.2 keV/μm左右, 此时所对应的碳离子能量约为35 MeV/u。 这些结果表明, C离子对粘红酵母菌的最佳致死效应和最佳致突变效应存在于不同的能量区域。 To evaluate inactive and mutagenic effects of carbon beam at different LET, the inactivation cross section and mutation cross section induced by carbon beams of different LET values were investigated in a red yeast strain Rhodotorula glutinis AY 91015. It was found that the maximum inactivation cross section of 4.37μm2 , which was very close to the average nucleus cross section, was at LET of 120.0 keV/μm. The maximum mutation cross section was at LET of 96.0 keV/μm. Meanwhile, the highest mutagenicity of carbon ion was found around 58.2 keV/μm. It implied that the most efficient LET to induce mutation in survival yeasts was 58.2 keV/μm, which corresponded to energy of 35 MeV/u carbon beam. The most effective carbon beam to induce inactivation and mutation located at different energy region. 相似文献
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V. N. Bagratashvili A. N. Konovalov A. A. Novitskiy M. Poliakoff S. I. Tsypina 《Russian Journal of Physical Chemistry B, Focus on Physics》2009,3(8):1154-1164
Fiber optic reflectometry (FOR) and scanning electron microscopy (SEM) were used to study the regularities of the etching
of a single-mode optical silica fiber with a germanium silicate core in subcritical and supercritical water. It was demonstrated
that the rate of etching of the germanium silicate core, being higher than that of etching of the silica cladding, was responsible
for the formation of a well at the fiber end face, the depth of which increased with the time of etching. The temporal behavior
of the FOR signal was of oscillatory character, an observation that accounted for the interference effects that accompany
the reflection of radiation (from the photodiode used in the FOR) from the fiber end face during its etching (well deepening).
The interference-controlled character of the FOR signal made it possible to directly measure the rate of etching of the fiber
end face in water in its different phase states (gaseous, liquid, and supercritical) at various temperatures and pressures.
The lowest measured rate of etching of the germanium silicate core (at 200°C and 54 atm) was 10−3 nm/s, whereas the highest measured rate was 30 nm/s (at 400°C and 246 atm). The temperature dependence of the etching rate
was demonstrated to obey the Arrhenius law, with an activation energy of 58 ± 3 kJ/mol. At later stages of etching, the FOR
signal changed from regular oscillatory to irregular noisy due to the formation defects of various sizes, as could be clearly
seen in SEM images. 相似文献