共查询到19条相似文献,搜索用时 125 毫秒
1.
利用飞秒脉冲激光和泵浦-探测技术测量了贵金属-介质复合薄膜(Cu-Ba-O、Au-Ba-O)的瞬态光学透过率随延迟时间的变化曲线,观察到了薄地光的吸收迅速增大并在皮秒时间内的状的现象,该现象是薄膜中超微粒子内费米能级附近电子被飞秒激光脉冲激光,产生非平衡态电子而经历瞬态弛豫造成的,本文从理论上给出了复合薄膜中Au超微粒子的电子声子相互作用常数g的数值。 相似文献
2.
采用微观双曲两步热传导模型,研究了飞秒脉冲激光加热过程中多层金属薄膜的热响应。利用界面连续条件,推得三层金属薄膜各层薄膜内电子温度和晶格温度在拉普拉斯域内的解析表达式。通过拉普拉斯数值反变换,计算并绘制了100nm单层Au膜和34nmAu/33nmCr/33nmAu三层膜在飞秒脉冲激光加热过程中各层薄膜内电子温度和晶格温度沿薄膜厚度的分布曲线。数值结果表明,激光加热过程中不仅电子与晶格之间存在强烈的非平衡热行为,不同金属材料薄膜界面上金属晶格温度也具有急剧的非平衡行为。同时讨论了多层薄膜温度分布特点及其与薄膜材料参数的关系。 相似文献
3.
随着激光技术的发展,人们能获得的激光脉冲越来越短,这样,可以对物质在飞秒领域的超快现象进行直接的瞬态弛豫研究.超快光脉冲与物质的相互作用是科学与技术的一个前沿领域,利用超短激光脉冲诱导出样品中的非平衡态载流子,测量样品的瞬态光谱的变化是近年来发展的一种研究样品中非平衡态电子声子弛豫的新技术.在超快激光脉冲作用下引起样品瞬态光学透过率随时间变化的测量中,使用了飞秒脉冲激光器、泵浦-探测(PumP-Probe)技术、计算机控制的光学延迟线、锁定放大器及数据采集系统.激光脉冲宽度为165fs,波长为647urn,脉冲重复… 相似文献
4.
5.
为了测量飞秒激光对多光谱滤波片的损伤阈值, 采用钛∶蓝宝石飞秒脉冲激光(800nm、50fs)对多光谱滤光片的前膜进行了激光损伤阈值的实验研究, 并使用显微镜观测了滤光片前膜的损伤形貌。结果表明, 薄膜在不同脉冲辐照次数(1, 2, 5和10)下, 前膜损伤阈值分别为1.68J/cm2, 1.56J/cm2, 1.44J/cm2和1.42J/cm2, 随着脉冲辐照次数的增加, 损伤阈值降低, 激光脉冲的重复辐射会对薄膜形成累积效应; 由于飞秒激光的宽度极短, 薄膜导带电子由多光子电离产生, 并迅速吸收激光能量, 当其能量大于材料的带隙能时, 会与价带电子发生碰撞产生另一个电子, 进而形成大量的自由电子, 对薄膜造成损伤; 在1-on-1和2-on-1测试方法下, 随着飞秒激光能量密度的增加, 前膜损伤区域的轮廓越来越清晰、规整, 并逐渐出现清晰的分层现象, 这归因于前膜干涉场的分布不同。该研究对多光谱滤波光膜在飞秒激光作用下的损伤效果提供了参考。 相似文献
6.
首先采用有限元法数值计算了铜膜内的电子温度和晶格温度分布变化,揭示了铜膜内电子非平衡热输运时间随飞秒激光光束参量的变化情况。仿真结果表明,铜膜内的电子非平衡热输运时间会随着泵浦光束数量及脉冲能量密度的增加而增加,并且使用三束飞秒泵浦激光作用时,电子非平衡热输运时间比单脉冲作用时的电子非平衡热输运时间增加了3倍。其次使用三束飞秒激光泵浦的泵浦-探测实验系统进行验证。实验结果表明:通过用具有一定延时的三束飞秒泵浦激光作用铜膜时,铜膜表面的瞬态反射率出现三次突变,使电子非平衡热输运时间得到极大延长,从而大幅度消除激光加工热障,并提高加工的质量、精度和效率。 相似文献
7.
8.
飞秒激光与金属作用后,电子被瞬间加热,电子温度将远远高于声子温度,并逐渐将能量传递给声子,这种非平衡过程中电子和声子间传热能力由电子-声子耦合系数表征。而到目前为止电子-声子耦合系数是否存在尺度效应还存在争议。采用飞秒激光抽运-探测法对金纳米薄膜非平衡传热过程进行了研究,利用抛物两步模型对实验数据进行拟合。通过对不同厚度的金纳米薄膜的电子-声子耦合系数的比较,研究表明,电子-声子耦合系数随着薄膜厚度的增加而减小。实验结果与已报道的基于电子自由程提出的理论模型所预测的变化趋势相一致。 相似文献
9.
实验研究了不同脉冲能量的飞秒激光诱发硅PIN光电二极管瞬态响应信号的特性。发现了探测器响应瞬态响应信号相继出现了三个明显的相位,深入讨论了飞秒激光诱发的高注入载流子在瞬态响应信号演化过程中所起的作用。结果表明,高注入载流子产生的空间电荷屏蔽效应是导致瞬态响应信号呈现三个相位的主要因素,它导致瞬态响应信号的持续时间主要取决于载流子双极扩散的速度。增加飞秒激光的脉冲能量会进一步延长探测器瞬态响应信号的持续时间。因此,飞秒激光会削弱探测器的工作性能,尤其是在高速信号探测中的工作性能。 相似文献
10.
通过搭建飞秒时间分辨的泵浦探测阴影成像系统,研究了聚焦的飞秒激光脉冲产生空气等离子体的瞬态演化特性,并对不同聚焦条件下空气等离子体的时间特性进行了数值模拟。实验结果表明:聚焦的飞秒激光电离空气等离子体的电子瞬态密度峰值先升高后缓慢下降;同时得到了高时间分辨下的电离速度变化与电子数密度的空间分布。计算结果显示:更高的单脉冲能量对应更高的饱和电子数密度,高数值孔径聚焦条件下隧穿电离也更早出现,表明飞秒时间分辨的泵浦探测阴影成像可为超快激光微加工的瞬态过程提供观测手段,同时可对超快激光微加工过程中的等离子屏蔽效应提供机理解释与加工工艺的优化参考。 相似文献
11.
Jie Li Wenbo Hu Qiang Wei Shengli Wu Xing Hua Jintao Zhang 《Journal of Electronic Materials》2017,46(3):1466-1475
As a type of electron-induced secondary electron emitter, MgO/Au composite thin film was prepared by reactive magnetron sputtering of individual Mg target and Au target, and the effects of key process parameters on its surface morphology and secondary electron emission (SEE) properties were investigated. It is found that to deposit a NiO buffer layer on the substrate is conducive to the subsequent growth of MgO grains owing to the lattice matching. The gold addition can raise the electrical conductivity of MgO film and further suppress the surface charging. However, the gold deposition would interfere with the MgO crystallization and increase the surface roughness of MgO/Au film. Therefore, MgO/Au composite thin film with a NiO buffer layer and proper deposition times of MgO and Au can achieve superior SEE properties due to good MgO crystallization, low surface roughness and reasonable electrical conductivity. The optimized MgO/Au composite thin film has a higher SEE coefficient and a lower 1-h SEE degradation rate under electron beam bombardment in comparison with MgO film. 相似文献
12.
A simple approach is proposed to enhance the electrical conductivity of olivine‐structured LiFePO4 thin films by uniformly dispersing small fractions of highly conductive silver (ca. 1.37 wt %) throughout the LiFePO4 film. In this approach, a highly densified (>85 %) LiFePO4–Ag target was first fabricated by coating conductive silver nanoparticles onto the surfaces of hydrothermally synthesized LiFePO4 ultrafine particles by a soft chemical route. Pulsed laser deposition (PLD) was then employed to deposit LiFePO4–Ag composite thin films on the Si/SiO2/Ti/Pt substrates. The PLD experimental parameters were optimized to obtain well‐crystallized and olivine‐phase pure LiFePO4–Ag composite thin films with smooth surfaces and homogeneous thicknesses. X‐ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectrometry (Raman), X‐ray photoelectron spectroscopy (XPS), DC conductivity measurements, cyclic voltammetry(CV), as well as galvanostatic measurements were employed to characterize the as‐obtained LiFePO4–Ag composite films. The results revealed that after silver incorporation, the olivine LiFePO4 film cathode shows a superior electrochemical performance with a good combination of moderate specific capacity, stable cycling, and most importantly, a remarkable tolerance against high rates and over‐charging and ‐discharging. 相似文献
13.
14.
高功率的激光系统对光学元件的抗激光损伤性能的要求不断提高。主要研究薄膜在脉冲激光诱导作用下的损伤特性及其机理,实验采用YAG脉冲激光器对TiO2/SiO2薄膜样片进行1-on-1方式的激光诱导。实验结果表明:采用低能量激光诱导对薄膜的光学透过率影响不大。经低能量激光诱导后,薄膜的表面结构缺陷得以修复,表面结构趋于完整,变得均匀和细腻。脉冲激光诱导TiO2/SiO2薄膜样片,激光能量阶较小时,其损伤阈值随能量增加而增加,损伤阈值最大可增加1倍;激光能量阶较大时,其损伤阈值随能量增加而减小。 相似文献
15.
16.
The reflectivity versus incident angle of a GaP/Au reflector,a GaP/SiO_2/Au triple ODR(omni-directional reflector) and a GaP/ITO/Au triple ODR was calculated.Compared to AlGaInP LEDs with a GaAs absorbing substrate, thin film LEDs with a Au reflector,a SiO_2 ODR and an ITO ODR were fabricated.At a current of 20 mA,the optical output power of four samples was respectively 1.04,1.14,2.53 and 2.15 mW.The Au diffusion in the annealing process reduces the reflectivity of the Au/GaP reflector to 9%.The differe... 相似文献
17.
S. C. Wang C. M. Wang C. Wang H. L. Chang Y. K. Tu C. J. Hwang S. Chi W. H. Wang Y. D. Yang W. H. Cheng 《Journal of Electronic Materials》1996,25(11):1797-1800
The effect of a thin film coating of Au on the joint strength, weld width, and penetration depth in laser welding techniques
for Invar-Invar packages is investigated experimentally. It is found that the joint strength, weld width, and penetration
depth are strongly dependent on the coating of Au thickness on the Invar material. The welded joints with thick Au coating
show narrower weld width, shallower penetration, and hence less joint strength than those of the packages with thin Au coating.
The increase in both the thermal conductivity and the vapor volume in the welded joints as the coating of Au thickness increases
are the possible mechanisms for the reduction. Detailed knowledge of the effect of thin film coatings of Au on the welded
materials, which gives both the highest joint strength and good adhesion, is essential for practical design and fabrication
of reliable optoelectronic packaging. 相似文献
18.
Ultrasensitive and Stable Au Dimer‐Based Colorimetric Sensors Using the Dynamically Tunable Gap‐Dependent Plasmonic Coupling Optical Properties 下载免费PDF全文
Dilong Liu Lingling Fang Fei Zhou Huilin Li Tao Zhang Cuncheng Li Weiping Cai Zhaoxiang Deng Liangbin Li Yue Li 《Advanced functional materials》2018,28(18)
A novel Au dimer‐based colorimetric sensor is reported that consists of Au dimers to a chitosan hydrogel film. It utilizes the ultrasensitively gap‐dependent properties of plasmonic coupling (PC) peak shift, which is associated with the dynamical tuning of the interparticle gap of the Au dimer driven by the volume swelling of the chitosan hydrogel film. The interparticle gap and PC peak shift of the Au dimer can be precisely and extensively controlled through the pH‐driven volume change of chitosan hydrogel film. This colorimetric sensor exhibits a high optical sensitivity and stability, and it works in a completely reversible manner at high pH values. Importantly, the sensitivity of the composite film can be tuned by controlling the crosslinking time of the composite film, and thus leading to a wide dynamic tuning sensitive range for different applications. This presented strategy paves a way to achieve the construction of high‐quality colorimetric sensors with ultrahigh sensitivity, stability and wide dynamic tuning sensitive range. 相似文献
19.
《Photonics Technology Letters, IEEE》2009,21(4):221-223