共查询到20条相似文献,搜索用时 140 毫秒
1.
2.
3.
4.
对超短超强激光脉冲 (45fs,6× 10 17W /cm2 )与光致电离氦气形成的欠稠密等离子体相互作用中的二次谐波辐射进行了实验研究。测量了多种打靶强度的飞秒激光脉冲与不同气体密度氦气相互作用的二次谐波光谱 ,得到在欠稠密等离子体中二次谐波辐射与打靶激光能量的关系 ,分析了产生二次谐波辐射产生的物理机制 ,在考虑了强短脉冲激光电离气体产生的等离子体径向电子密度梯度因素 ,基于非线性作用过程的理论预期曲线与实验结果较好地吻合 相似文献
5.
6.
7.
在激光与物质相互作用的实验中,气体靶通常由超声速喷嘴在高背压下向真空中高速喷射气体产生。激光与气体靶相互作用时确定打靶条件对整个实验有着十分重要的意义。为了得到不同实验条件下气体靶密度的分布特性,采用马赫-曾德尔干涉法测量了气体靶密度分布,获取了干涉图样。使用基于傅里叶变换的条纹处理方法测得的干涉图样,得到不同实验条件下气体分子密度的全空间分布。实验表明:用M-Z干涉仪测量超声速气体喷嘴产生的气体靶密度分布十分有效。基于傅里叶变换的条纹处理方法具有精度高、实时性好的优点,为打靶时气体靶密度的实时测量提供了可能。 相似文献
8.
9.
在“星光Ⅱ”激光装置上对Mg/Al混合材料平面靶和Mg/Al示踪层金盘靶进行三倍频激光打靶实验,用平面晶体谱仪测量靶材料发射的X射线能谱,获取了示踪离子谱线实验数据.采用多组态Dirac-Fock方法计算所需原子参数,并在局域热动平衡条件下建立了双示踪离子谱线强度比随电子温度变化关系.在此基础上由双示踪元素等电子谱线法确定了Mg/Al混合材料平面靶及金盘靶激光等离子体的电子温度
关键词:
电子温度
激光等离子体
X射线能谱 相似文献
10.
本文叙述用一维非平衡辐射流体力学激光打靶程序模拟计算高功率密度(~1013W/cm2)激光照射中Z介质薄靶形成的等离子体状态。考虑的物理过程有轫致、光电离、电子碰撞电离及它们的逆过程,Compton散射过程等。Compton散射采用Fokker-Planck近似;电子和离子热传导采用限流扩散近拟;光子方程采用多群限流扩散近似;用平均原子模型计算布居数。激光的吸收主要考虑逆轫致吸收。用功率密度分别为5×1013W/cm2和1×1014W/cm2,波长0.53μm,脉宽450ps的激光从两面和单面打se薄靶,模拟计算结果与国外的实验结果[1]一致。 相似文献
11.
根据能量平衡原理,导出了脉冲激光作用靶材的烧蚀率公式,并根据流体动力学理论,得出了脉冲激光产生的等离子体的空间运动特性方程,将靶材烧蚀率公式与等离子体空间动力学方程结合起来,根据实验研究了不同激光功率密度和波长对Kta0.65Nb0.35O3(KTN)薄膜沉积特性的影响,得到了一些有价值的结果,并对结果进行了详细的讨论,理论计算结果与实验大体符合.
关键词:
PLD技术
烧蚀率
等离子体
KTN薄膜 相似文献
12.
Laser effects on the electronic states in GaAs/ Ga1−xAlxAs V-shaped and inverse V-shaped quantum wells under a static electric field are studied using the transfer matrix method. The dependence of the donor binding energy on the laser field strength and the density of states associated with the impurity is also calculated. It is demonstrated that in inverse V-shaped quantum wells under electric fields, with an asymmetric distribution of the electron density, the position of the binding energy maximum versus the impurity location in the structure can be adjusted by the intensity of the laser field. This effect could be used to tune the electronic levels in quantum wells operating under electric and laser fields without modifying the physical size of the structures. 相似文献
13.
In this paper high-order harmonic generation (HHG) spectra and the ionization probabilities of various charge states of small cluster Na2 in the multiphoton regimes are calculated by using time-dependent local density approximation (TDLDA) for one-colour (1064 nm) and two-colour (1064 nm and 532 nm) ultrashort (25 fs) laser pulses. HHG spectra of Na2 have not the large extent of plateaus due to pronounced collective effects of electron dynamics. In addition, the two-colour laser field can result in the breaking of the symmetry and generation of the even order harmonic such as the second order harmonic. The results of ionization probabilities show that a two-colour laser field can increase the ionization probability of higher charge state. 相似文献
14.
G. Yu. Grigor’ev L. I. Men’shikov P. L. Men’shikov Sh. Sh. Nabiev 《Russian Journal of Physical Chemistry B, Focus on Physics》2017,11(1):24-33
The collisionless vibrational excitation of a polyatomic molecule in an IR laser radiation field has been theoretically studied. It has been shown that (i) the degree of vibrational excitation (namely, number 0000 of vibrational quanta of a molecular mode near-resonant with the IR laser field that are absorbed by the molecule) is low if laser pulse intensity P (energy flux density in the laser beam) is lower than a certain critical value P cr; (ii) the degree of excitation abruptly increases after crossing the boundary where P = P cr; (iii) this effect is attributed to two properties inherent in polyatomic molecules, namely, the anharmonicity of the vibrational mode interacting with the laser field and the energy exchange with other modes; and (iv) at P > P cr, number 00000 is determined only by energy density Φ = PτP, where τP is the laser pulse duration, 00000 monotonically increases with increasing Φ. The model is in good agreement with the experimental data. 相似文献
15.
In this paper, gold-coated gratings for pulse compression have been prepared and their laser damage experiments have been performed. Varied laser damage morphologies have been observed: when a 60 fs-pulsed laser with energy density slightly higher than the damage threshold was used, damage morphology with a characteristic of discrete distribution of small pits was appeared. These damage pits are linearly distributed at the junction of ridges and grooves. If the laser energy density is much higher than the damage threshold, the gold films was overall ablated and the grating structure disappeared. Besides, if the gold film has poor adhesion, it was peeled off. When a 450 ps-pulsed laser with energy density slightly higher than the damage threshold was used, part of grating ridges will be ablated and an obvious line exists between the ablated area and the unchanged area. In theory, the laser induced temperature field and stress field in gold-coated gratings were calculated based on the electromagnetic field using the finite element method. It is demonstrated that the temperature and thermal stress distribution characteristics are affected by the laser heating rate and the heat diffusion time (the calculated diffusion time ranges from 6 fs to 450 ps), which determines the laser damage characteristics. The possible damage drivers have electron hydrodynamic pressure, thermal ablation and thermal stress. 相似文献
16.
17.
F. Reichert M. Fechner P. Koopmann C. Brandt K. Petermann G. Huber 《Applied physics. B, Lasers and optics》2012,108(3):475-478
We report on crystal growth, spectroscopic investigations, crystal field tuning, and laser experiments of neodymium doped mixed sesquioxides (Lu1?x Sc x )2O3. Crystals were grown by the Nacken?CKyropoulos and the Heat-Exchanger method. Emission spectra for several mixing ratios are presented. Cw laser experiments were carried out with a 0.35?at.%-doped Nd:Lu1.82Sc0.18O3 crystal by using a Ti:sapphire laser as pump source, achieving a maximum slope efficiency of 47?% with respect to the absorbed pump power and a maximum output power of 356?mW at a wavelength of 952.7?nm. To the best of our knowledge, this represents the first continous wave (cw) laser operation of a Nd-doped mixed sesquioxide. 相似文献
18.
The two or multi-mode optically pumped NH3 FIR laser had been studied theoretically. The NH3 molecular gas was assumed to be a three-level system and obeyed the time-dependent behavior of the density matrix equations. Considering the situation of playing the two or multi-mode optical pumping and the FIR laser field were same polarized. The gain coefficient and the output FIR power of the system could be calculated by using the iteration method.It had been predicted that the two or multiple longitudinal mode optically pumped NH3 FIR laser could have a greater output power or higher lasing efficiency than single mode pumped FIR laser under suitable selected operating parameters of laser.Supported by The Education Foundation of PRC. 相似文献
19.
Nonlinear absorption of CO2 laser pulses at the multi-MW level has been studied in n-type germanium at room temperature. This nonlinear absorption limits the level of CO2 laser intensity that can be transmitted through an optical grade germanium crystal. The observed nonlinearity may be interpreted in terms of nonequilibrium electron-hole pairs generated by hot electrons created by the intense laser field. The number of nonequilibrium carriers generated is measured by photoconductivity experiments, and the results are correlated to the absorption measurements. 相似文献
20.
Dattatray J. Late Mahendra A. More Sucharita Sinha K. Dasgupta Pankaj Misra B. N. Singh Lalit M. Kukreja Sudha V. Bhoraskar Dilip S. Joag 《Applied Physics A: Materials Science & Processing》2011,104(2):677-685
The paper deals with the comparative study of nanocrystalline Lanthanum hexaboride (LaB6) thin films grown on various substrates by Pulsed laser deposition and Arc plasma method. Field emission studies were carried
out on LaB6 films deposited on various substrates show metallic behavior of the emitters. The high value of field enhancement factors,
indicating that the electron emission from LaB6 nanoscale protrusions deposited on emitter surface. The post field emission surface morphology of the emitters showed no
significant erosion of the films during continuous operation. The observed behavior indicates that it is linked with the growth
of LaB6 films on substrate crystal structure. The LaB6 nanocrystallites/nanowires films were synthesized using arc plasma method shows good emission current stability. The LaB6 micro/nanocrystallites were also obtained by picosecond laser irradiation which gives high enhancement β factor, and good emission current stability along with high current density. The results reveal that nanocrystalline LaB6 films, exhibit high resistance to ion bombardment and excellent structural stability and are more promising emitters for
practical applications in field emission based new generation devices. 相似文献