共查询到20条相似文献,搜索用时 15 毫秒
1.
A. A. Ionin S. I. Kudryashov S. V. Makarov L. V. Seleznev D. V. Sinitsyn 《JETP Letters》2011,94(1):34-38
Superstrong shock waves of multimegabar level generated during ablation of an aluminum surface by intense (<1 PW/cm2) femtosecond laser pulses have been detected by observing the propagation of a shock wave in air from the ablated surface
to a broadband piezoelectric receiver. The estimated initial pressure and velocity of the shock wave (ablation plume) agree
well with data obtained earlier by various methods for shock waves propagating inside ablated targets. 相似文献
2.
3.
Mikhail E. Povarnitsyn Tatiana E. Itina Pavel R. LevashovKonstatntin V. Khishchenko 《Applied Surface Science》2011,257(12):5168-5171
In this paper, we study the mechanisms of femtosecond double-pulse laser ablation of metals. It was previously shown experimentally that the crater depth monotonically drops when the delay between two successive pulses increases. For delays longer than the time of electron-ion relaxation the crater depth can be even smaller than that produced by a single pulse. The results of the performed hydrodynamic simulation show that the ablation can be suppressed due to the formation of the second shock wave. The modeling results of the double-pulse ablation obtained for different delays correlate with the experimental findings. 相似文献
4.
When the femtosecond laser focused in the water, the breakdown will be induced. The generated high-speed jet and shock wave can be used to etch silica glass for fabricating three-dimensional (3D) microfluidic chips. We present a simple and practical method to produce 3D multilayer microfluidic chips in silica glass. This method offers high design flexibility and fabricating feasibility. We also introduce a convenient cleaning method for diluting and ejecting the ablated debris from microchannel. Therefore, the femtosecond laser induced high-speed jet and shock wave can be used to fabricate complex microfluidic chips in silica glass. Experimental results show that the diameter of microchannel is uniform and the complexity of the microfluidic chip is under control. As a proof of principle, we demonstrate the feasibility of the fabricating process by using the water-assisted femtosecond laser ablation. 相似文献
5.
We report a direct observation of the temperature field on a steel specimen during ablation by multiple femtosecond laser pulses using an infrared thermography technique. From the experimental results and simulation study of the temperature field, we quantified the deposited thermal power into the specimen during the ablation process. We found that more than two thirds of the incident laser power was deposited in the steel specimen when ablated by multiple femtosecond laser pulses. This result provides further understanding of the heating effect in materials processing by ultrashort laser pulses. 相似文献
6.
Nanoparticles were synthesized by irradiating a nickel target with femtosecond laser pulses in high vacuum, and subsequently analyzed. The proof-of-principle experiments aim to modify the size characteristics of the produced nanoparticles. For nickel it is found that: (i) ultraviolet laser pulses lead to a remarkable change in the nanoparticles size distribution with respect to visible laser pulses; (ii) irradiation of the femtosecond pulses induced ablation plume with a second, delayed ultraviolet laser pulse can change the size characteristics of the produced nanoparticles. 相似文献
7.
8.
M. A. Garasev A. I. Korytin V. V. Kocharovsky Yu. A. Mal’kov A. A. Murzanev A. A. Nechaev A. N. Stepanov 《JETP Letters》2017,105(3):164-168
The appearance of a density bump is experimentally revealed in an electrostatic shock wave during the ablation of an aluminum foil by a femtosecond laser pulse. The numerical simulation shows that this phenomenon can be explained by the generation of a packet of ion acoustic waves under the action of high-energy electron flows in a collisionless plasma. It is found that, for the formation and maintenance of the dense plasma layer in the shock wave, the contributions of accelerated ions overtaking it and wave-captured ions of the background plasma formed by a nanosecond laser prepulse in the process of ablation are significant. 相似文献
9.
Aivaras Urnie?ius Nerijus ?iaulys Via?eslav Kudria?ov Valdas Sirutkaitis Andrius Melninkaitis 《Applied Physics A: Materials Science & Processing》2012,108(2):343-349
We studied evolution of femtosecond laser ablation by employing novel method of time-resolved off-axis digital holographic microscopy. Phase and amplitude profiles of early shock front and ablation plume dynamics of irradiated tempered steel were reconstructed from the digital holograms. In order to gain additional information, digital holographic microscopy was combined with plasma emission imaging. By using both techniques simultaneously we studied material response to multi-pulse irradiation, shock wave propagation, ablation plume formation and plasma emission. The significant changes in ablation performance were observed when using multi-pulse irradiation if compared to widely investigated single-shot regime. 相似文献
10.
S. Canulescu E. Papadopoulou D. Anglos T. Lippert M. J. Montenegro S. Georgiou M. D?beli A. Wokaun 《Applied Physics A: Materials Science & Processing》2011,105(1):167-176
Thin films of La0.6Ca0.4CoO3 were grown by pulsed laser ablation with nanosecond and femtosecond pulses. The films deposited with femtosecond pulses (248 nm,
500 fs pulse duration) exhibit a higher surface roughness and deficiency in the cobalt content compared to the films deposited
with nanosecond pulses (248 nm, 20 ns pulse duration). The origin of these pronounced differences between the films grown
by ns and fs ablation has been studied in detail by time-resolved optical emission spectroscopy and imaging. The plumes generated
by nanosecond and femtosecond ablation were analyzed in vacuum and in a background pressure of 60 Pa of oxygen. The ns-induced
plume in vacuum exhibits a spherical shape, while for femtosecond ablation the plume is more elongated along the expansion
direction, but with similar velocities for ns and fs laser ablation. In the case of ablation in the background gas similar
velocities of the plume species are observed for fs and ns laser ablation. The different film compositions are therefore not
related to different kinetic energies and different distributions of various species in the plasma plume which has been identified
as the origin of the deficiency of species for other materials. 相似文献
11.
P. Gregorčič J. Zadravec J. Možina M. Jezeršek 《Applied Physics A: Materials Science & Processing》2014,117(1):353-357
In this investigation, we used high-speed shadow photography to observe fast optodynamic phenomena such as shock waves and the ablation of flat metal surfaces. These phenomena were induced in air by a Q-switched Nd:YAG laser (λ = 1,064 nm) with a pulse duration of 4 ns and an excitation pulse energy between 10 and 55 mJ. For a good spatial resolution of the shadowgraphs, we used short illumination pulses (30 ps) from a frequency-doubled Nd:YAG laser (λ = 532 nm). Using the shadowgraphs of the shock wave expansion into a half-space, we measured the optodynamic energy conversion efficiency, defined as the ratio between the mechanical energy of the shock wave and the excitation pulse energy. This efficiency increases with an increasing excitation pulse energy. We also present the characteristic shadowgraphs of the ablation of a black-painted metal surface, where the macroscopic material particles are clearly visible. They follow the shock wave and eventually overtake it. As a result, the shape of the shock wave, which normally expands concentrically into the half-space, has an altered form. The presented results reveal the phenomenon of the laser ablation of coated metal surfaces. 相似文献
12.
采用1 kHz,800 nm,50 fs—24 ps的钛宝石激光脉冲对单晶硅样品在空气和水溶液环境中的烧蚀加工特性进行了研究.实验观察到了超短脉冲激光在空气氛围中烧蚀形成的双层环状结构,分析揭示了加工区域中心和边缘的烧蚀物理机制分别为热熔化和库仑爆炸,并测量了双层环状结构半径随入射激光能量、脉冲数及持续时间等的变化关系,结果表明获取较大深-宽比的加工效果需选择小能量脉冲激光的多次作用.在水溶液环境中,实验发现飞秒激光在样品表面诱导产生了亚微米量级的多孔状结构,而皮秒激光则更容易实现对硅表面的非热性去除.这是由于激光诱导的光机械应力和空泡效应随脉冲宽度变大而增强所致,在实验上确立了区分这两种不同加工状态的临界脉冲宽度.
关键词:
飞秒激光
硅片
激光加工 相似文献
13.
We have performed a comparative study of UV laser ablation of SrTiO3 with nanosecond- and sub-picosecond sources, respectively. The experiments were performed with lasers at a wavelength of 248 nm and pulse durations of 34 ns and 500 fs. Femtosecond ablation turns out to be more efficient by one order of magnitude and eliminated the known problem of cracking of SrTiO3 during laser machining with longer pulses. In addition, the cavities ablated with femtosecond pulses display a smoother surface with no indication of melting and well-defined, sharp edges. These effects can be explained by the reduced thermal shock effect on the material by using ultrashort pulses. 相似文献
14.
Qiang Li Huiying Lao Jia Lin Yuping Chen Xianfeng Chen 《Applied Physics A: Materials Science & Processing》2011,105(1):125-129
In this paper, a 3D two-temperature model is introduced to investigate femtosecond ablation on aluminum film. 3D temperature
evolutions for both electrons and lattice are obtained, which present us a vivid view of the energy transformation process
during femtosecond ablation. Simulated 3D ablation craters irradiated by a single pulse with different energy are acquired,
from which we can easily and precisely predict crater depth and radius before ablation takes place. In the experiment we measure
the radii of the craters ablated by pulses with different energy and numbers delivered from a chirped pulse amplification
Ti: sapphire system. The threshold fluence for both single and multi pulses are obtained. Comparisons are made between results
of the experiment and relative simulated calculations show the reliability of our proposed calculation model. 相似文献
15.
16.
E. V. Barmina C. Fotakis P. A. Loukakos E. Stratakis G. A. Shafeev 《Applied Physics A: Materials Science & Processing》2014,116(1):359-364
Formation of surface nanostructures on a Silicon target immersed into liquids is experimentally studied under its ablation by femtosecond laser pulses. Nanotexturing of Silicon upon its exposure to delayed femtosecond pulses and double exposure method is investigated. Two different types of morphological features are observed, namely periodic ripples and nanostructures. Field emission scanning electron microscopy shows that the density of nanostructures as well as their morphology depends on such parameters as fluence and the delay time between pulses and reaches its maximum at delay of 1 ps. Two-dimensional homogenous array of nanostructures is formed by laser ablation in liquids using double-exposure method. Possible applications of generated nanostructures are discussed. 相似文献
17.
Yu. V. Afanasiev B. N. Chichkov N. N. Demchenko V. A. Isakov I. N. Zavestovskaya 《Journal of Russian Laser Research》1999,20(2):89-115
Laser ablation of metals by femto- and picosecond pulses is analytically and numerically studied within the framework of the
plasma model for the ablated material. Ablation is initiated by high-power thermal and hydrodynamic waves which propagate
into the irradiated material. Analytical expressions for the thermal ablation and for the ablation by the shock wave are obtained.
Numerical simulations with the computer code RAPID are in good agreement with analytical results.
Translated from Preprint No. 64 of the P. N. Lebedev Physical Institute, Moscow (1996). 相似文献
18.
Field-free molecular orientation induced by combined femtosecond single- and dual-color laser pulses:The role of delay time and quantum interference 下载免费PDF全文
The coherent control of field-free molecular orientation of CO with combined femtosecond single- and dual-color laser pulses has been theoretically studied. The effect of the delay time between the femtosecond single- and dual-color laser pulses is discussed, and the physical mechanism of the enhancement of molecular orientation with pre-alignment of the molecule is investigated. It is found that the basic mechanism is based on the creation of a rotational wave packet by the femtosecond single-color laser pulse. Furthermore, we investigate the interference between multiple rotational excitation pathways following pre-alignment with femtosecond single-color laser pulse. It is shown that such interference can lead to an enhancement of the orientation of CO molecule by a factor of 1.6. 相似文献
19.
Nonlinear micromachining with femtosecond laser pulses has attracted much attention in microphotonics and biophotonics. In this paper, we demonstrate the fabrication of optical elements in bulk transparent materials, direct welding between transparent substrates, and subcellular ablation in living cells by focusing femtosecond laser pulses. 相似文献
20.
Shock-wave generation upon axicon focusing of femtosecond laser radiation in transparent dielectrics
A. A. Babin A. M. Kiselev D. I. Kulagin K. I. Pravdenko A. N. Stepanov 《JETP Letters》2004,80(5):298-302
It is shown experimentally that the axicon focusing of intense femtosecond laser pulses in transparent dielectrics leads to efficient excitation of shock waves. A method is developed for measuring the dynamics of shock waves, which uses a frequency-chirped probe pulse and has high spatial (~1 μm) and time (~10 ps) resolutions. The initial stage of the evolution of an intense (up to 10 GPa) shock wave is studied by this method. 相似文献