共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Aggoune F. Vidal E. H. Amara 《Applied Physics A: Materials Science & Processing》2010,101(1):167-171
The interaction between a laser-produced aluminum plasma and the ambient air, at a pressure of 173.3 Pa, is studied at the
plasma thermalization stage. A two-dimensional approach is developed to solve the Navier–Stokes equations, where a finite
volume discretization allows for obtaining a numerical solution. The simulation runs over a time representing 10 μs of plasma
expansion. It is shown that the shock and drag models are good approximations for the two successive regimes after the initial
strong expansion stage, and the calculation makes evident the plume sharpening on the axial direction before its confinement
by the ambient gas, which is in good agreement with the experimental observation. 相似文献
2.
Joseph P. Moening Sachin S. Thanawala Daniel G. Georgiev 《Applied Physics A: Materials Science & Processing》2009,95(3):635-638
We report on the formation of microbumps and high-aspect-ratio protrusions on gold films as a result of single-pulse localized
laser irradiation. The laser source employed in this work is a Q-switched nanosecond-pulse laser, emitting at its fourth harmonic
of 266 nm. Gold films with a thickness of several hundred nanometers were irradiated in ambient or under low-vacuum conditions,
with circular laser spots, several micrometers in diameter. A mask projection technique was used to generate these spot patterns.
The resulting structures were imaged via scanning electron microscopy. The formation mechanism of these structures is briefly
discussed in view of our results and other, related published work. 相似文献
3.
Tomohiko Nakajima Tetsuo Tsuchiya Toshiya Kumagai 《Applied Physics A: Materials Science & Processing》2008,93(1):51-55
Ca0.997Pr0.002TiO3 (CPTO) thin films that show strong red luminescence were successfully prepared by means of an excimer laser assisted metal
organic deposition (ELAMOD) process with a KrF laser at a fluence of 100 mJ/cm2, a pulse duration of 26 ns, and a repetition rate of 20 Hz at 100°C in air. The CPTO films grew on the silica, borosilicate,
and indium-tin-oxide (ITO) glasses. The crystallinity of the CPTO films depended on the substrates; the films were well grown
on the borosilicate and ITO glasses compared to the silica glass. To elucidate the key factors for the crystallization of
the CPTO films in this process, we carried out numerical simulations for the temperature variation at the laser irradiation,
using a heat diffusion equation, and compared the experimental data with thermal simulations. According to the results, we
have shown that a large optical absorbance of the film and a small thermal conductivity of the substrate provide effective
annealing time and temperature for the crystallization of the CPTO films, and polycrystalline intermediate layer which has
a large optical absorption such as the ITO also plays a key role for the nucleation of the CPTO crystals in the ELAMOD process. 相似文献
4.
Kuldeep Kumar P. Arun Chhaya Ravi Kant N. C. Mehra Vincent Mathew 《Applied Physics A: Materials Science & Processing》2010,99(1):305-310
Cesium metal clusters strongly affect the optical properties of cesium iodide thin films. The metal clusters are formed during
film formation by thermal evaporation. The cesium cluster of 30–40 nm in the matrix of cesium iodide insulating thin films
results in Surface Plasmon Resonance (SPR). The peak position of these SPR peaks showed a red shift. This was shown to be
due to changes in the dielectric constant of CsI resulting from the strains in the films caused by the metal clusters themselves. 相似文献
5.
S. Lazare R. Bonneau S. Gaspard M. Oujja R. De Nalda M. Castillejo A. Sionkowska 《Applied Physics A: Materials Science & Processing》2009,94(4):719-729
Self standing films of biopolymers like gelatine, collagen, and chitosan irradiated with single nanosecond or femtosecond
laser pulse easily yield on their surface, a nanofoam layer, formed by a cavitation and bubble growth mechanism. The laser
foams have interesting properties that challenge the molecular features of the natural extracellular matrix and which make
them good candidates for fabrication of artificial matrix (having nanoscopic fibers, large availability of cell adhesion sites,
permeability to fluids due to the open cell structure). As part of the mechanistic study, the dynamics of the process has
been measured in the nanosecond timescale by recording the optical transmission of the films at 632.8 nm during and after
the foaming laser pulse. A rapid drop 100→0% taking place within the first 100 ns supports the cavitation mechanism as described
by the previous negative pressure wave model. As modeled a strong pressure rise (∼several thousands of bar) first takes place
in the absorption volume due to pressure confinement and finite sound velocity, and then upon relaxation after some delay
equal to the pressure transit time gives rise to a rarefaction wave (negative pressure) in which nucleation and bubble growth
are very fast. 相似文献
6.
I.IntroductionThegenerationofacousticpulsebylaserirradiationofametalsurfacewasfirstsuggestcdbyWhitein1963[1l.SincethatdateLaserU1trasoundtechniquchasbeendcvclopedrapidly.Becausethistechniquehasanumberoftechnicalfcatures,suchasnon-contact,highbandwidth,highhme-spacia1resolution,quantitativeteshng,generationoflongitudinal,shcarandRay1cighwaves(simu1taniously),andsoon,ithasbccnwidelyapp1icdtomcasurementsofmatcrialproperties,detectionofdefects,andcalibrationoftransd.ccrsl'-'o].Inordertodcve1opth… 相似文献
7.
S. I. Anisimov N. A. Inogamov Y. V. Petrov V. A. Khokhlov V. V. Zhakhovskii K. Nishihara M. B. Agranat S. I. Ashitkov P. S. Komarov 《Applied Physics A: Materials Science & Processing》2008,92(4):797-801
The mechanical action of laser exposure on a foil may result in the ablation of irradiated front layer and the rear-side spallation.
The dynamics of an Al foil is studied by means of two-temperature (2T) hydrodynamics and molecular dynamics (MD). It is found
that the rear-side spallation threshold F
s exceeds the front-side ablation threshold F
a. We propose to extend the common approach in laser-matter experiments by pump–probe measuring of the rear-side displacement. 相似文献
8.
Simultaneous compression of the pulsewidth and the pulse train of a passivelymode-locked Nd:YAG laser has been achieved by using a plano-convex unstable resonatorwith a nonlinear Sagnac ring interferometer.A single pulse energy of >30mJ and apulsewidth of ≤10ps have been obtained.Using this system,the LAGEOS and ETALONsatellites laser ranging have been performed successfully. 相似文献
9.
Y. Tao M. S. Tillack S. Yuseph R. Burdt F. Najmabadi 《Applied physics. B, Lasers and optics》2010,99(3):397-400
It was found that the electron density scale length of Sn plasma irradiated with a long duration CO2 laser pulse is much shorter than that predicted by the classical isothermal model. The experimentally observed small dominant
region of in-band (2% bandwidth) 13.5-nm extreme ultraviolet (EUV) emission coincides with this constrained hydrodynamic behavior.
The lower hydrodynamic efficiency may come from the strongly inhibited ablation mass and makes a CO2-laser-produced Sn plasma suitable as an EUV radiation source. 相似文献
10.
Zunshi Qu Yonggang Wang Jie Liu Lihe Zheng Liangbi Su Jun Xu 《Applied physics. B, Lasers and optics》2012,109(1):143-147
We demonstrated the first use of carbon nanotube as a saturable absorber in the Q-switched and Q-switched mode-locking of a diode pumped Tm:YAP operating at 2 μm. At the incident pump power of 8.64 W, the minimum Q-switched pulse width of 255.1 ns, and the maximum peak power 53.1 W can be obtained with the corresponding repetition rate of 21.76 kHz. The performance of a diode-pumped passively Q-switched mode-locked Tm:YAP laser with high repetition rate formed with a folded cavity. As high as 780 mW average output power was produced in QML laser. The repetition rate of the mode-locked pulse inside the Q-switched envelope was 244.1 MHz. The dependence of the operational parameters on the pump power was also investigated experimentally. 相似文献
11.
D. L. Sun J. Q. Luo J. Z. Xiao Q. L. Zhang H. H. Jiang S. T. Yin Y. F. Wang X. W. Ge 《Applied physics. B, Lasers and optics》2008,92(4):529-533
The influence of annealing treatments and gamma-ray irradiation on the absorption and fluorescence spectra of Cr:GSGG crystals
grown by the Czochralski method has been investigated. Two absorption bands located near 686 nm and 1050 nm were weakened
markedly after the crystal was re-annealed in H2 atmosphere, which is due to the Cr4+ ions being de-oxidized into Cr3+ ions. The other two weak additional absorption bands induced by gamma-ray irradiation appearing near 310 nm and 480 nm are
ascribed to the Fe2+ ions and F-type color centers, respectively. In particular, the gamma-ray irradiation with a dose of 100 Mrad has an effect
of improving slightly the luminescence properties of Cr:GSGG crystals. The improvement mechanism is analyzed and discussed. 相似文献
12.
Aaron Sellinger Elodie Leveugle James M. Fitz-Gerald Leonid V. Zhigilei 《Applied Physics A: Materials Science & Processing》2008,92(4):821-829
Coarse-grained molecular dynamics simulations are applied to investigate the origins of the surface features observed in films
deposited by the Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. The formation of transient balloon-like structures
with a polymer-rich surface layer enclosing matrix vapor, observed in earlier simulations of slow heating of polymer-matrix
droplets, has been explored in this work at higher rates of thermal energy deposition. Tensile stresses generated in the regime
of partial stress confinement are found to induce an internal boiling in the overheated droplets and associated generation
of “molecular balloons” at thermal energy densities at which no homogeneous boiling takes place without the assistance of
tensile stresses. Simulations of the dynamic processes occurring upon the collision of a polymer-matrix droplet with a substrate
provide the molecular-level pictures of the droplet impact phenomenon and reveal the connections between the droplet landing
velocity and the shapes of the polymer features observed in scanning electron microscopy images of films deposited in MAPLE
experiments. The distinct types of surface features observed in MAPLE experiments, namely, wrinkled “deflated balloons,” localized
arrangements of interconnected polymer filaments, and elongated “nanofibers,” are shown to emerge from different scenarios
of droplet landing and/or disintegration observed in the simulations. 相似文献
13.
Extremely intense laser field that makes nonlinear quantum vacuum can be generated by coherent superposition of multiple lasers in circular configuration that incorporates optical fibers synchronization scheme and piecewise mirrors in circular array operating below typical damage threshold. Coherent amplification and large laser beams can produce intensity reaching nonlinear quantum vacuum regime. The effects of phase jitter and envelope timing of the pulses due to imperfect synchronization are simulated and analyzed for both linear and circularly polarized pulses. We obtain simple analytical expressions that well describe the envelope jitter and phase jitter. Several practical aspects are discussed, including implications of scaling the laser dimension and pulse duration, with possibility for giant laser facility. 相似文献
14.
J. Faupel C. Fuhse A. Meschede C. Herweg H.U. Krebs S. Vitta 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1233-1235
Ceramic–metal (MgO combined with Fe, Ti and Ni80Nb20) and polymer–metal (polycarbonate combined with Ag and Pd) nanocomposite multilayers were deposited at room temperature by laser ablation (at 248 nm). The multilayers were characterized by X-ray reflectometry, infrared spectroscopy and transmission electron microscopy. In the case of MgO/metal multilayers, well-layered structures are produced down to layer periodicities of 1.2 nm, necessary for tunneling magnetoresistance devices and X-ray mirrors in the water window. The interface roughness in the case of polymer/metal multilayers is found to be a strong function of the metal layer thickness and also the nature of the metal. PACS 68.55.-a; 81.15.Fg 相似文献
15.
N. A. Inogamov S. I. Ashitkov V. V. Zhakhovsky V. V. Shepelev V. A. Khokhlov P. S. Komarov M. B. Agranat S. I. Anisimov V. E. Fortov 《Applied Physics A: Materials Science & Processing》2010,101(1):1-5
Ultrashort laser pulse transfers metal into a two-temperature warm dense matter state and triggers a chain of hydrodynamic
and kinetic processes—melting, expansion, stretching, creation of tensile stress and transition into metastable state. We
study the response of aluminum film deposited on a glass substrate to irradiation by a pump laser pulse transmitted through
glass. Several films with thicknesses from 350 to 1200 nm have been investigated. The smallest thickness is of the order of
the heating depth d
T∼100 nm in Al. The d
T-layer and the free rear side of the film are coupled through pressure waves propagating between them. Therefore, the processes
within d
T-layer affects the time dependent displacement Δ
x
rear(t) of the rear surface. We compare simulated and experimental dependencies Δ
x
rear(t) obtained by the pump–probe technique. It allows us to define a thickness of molten Al layer and explore the two-temperature
processes occurring inside the heated layer. 相似文献
16.
D. Nodop J. Rothhardt S. H?drich J. Limpert A. Tünnermann 《Applied physics. B, Lasers and optics》2009,94(3):399-401
We present a Q-switched microchip laser emitting 1064-nm pulses as short as 100 ps synchronized to a cavity dumped femtosecond
laser emitting 800-nm pulses as short as 80 fs. The synchronization is achieved by presaturating the saturable absorber of
the microchip laser with femtosecond pulses even though both lasers emit at widely separated wavelengths. The mean timing
jitter is 40 ps and thus considerably shorter than the pulse duration of the microchip laser. 相似文献
17.
This paper has solved the Chester modified heat conduction equation of the different relaxation time Υ value under different temperature conditions, different boundary conditions and the different initial conditions by different means of methods. These solutions can help to obtain temperature field of laser thermal effects. 相似文献
18.
F. Amrani A. Haboucha M. Salhi H. Leblond A. Komarov F. Sanchez 《Applied physics. B, Lasers and optics》2010,99(1-2):107-114
We investigate experimentally ordered and disordered pattern formation of solitons in a double-clad fiber laser. We point out an analogy between the different states of matter and the states of a set of dissipative solitons. In particular, we have identified a gas, a supersonic gas flow, a liquid, a polycrystal and a crystal of solitons. The different states are obtained only by adjustment of the intracavity phase plates. 相似文献
19.
T. Kobayashi T. Kato Y. Matsuo M. Kurata-Nishimura Y. Hayashizaki J. Kawai 《Applied Physics A: Materials Science & Processing》2008,92(4):817-819
We investigate the so-called “matrix effect” on the relative intensities of ions in mixed solutions of alkali salts by using
femtosecond laser ablation time-of-flight mass spectrometry (fsLA-TOFMS). For the 1:1 mixed solution of sodium and potassium
salts, the intensity ratio of cations (Na+/K+) decreases as the total concentration increases. From the measurement for the mixed solution of lithium, sodium, potassium,
rubidium, and cesium solutions, we find out significant dependence of each ion intensity on the total concentration. The results
suggest that the electron transfer from neutral atoms to cations coexistent in the ablation plasma affects the relative ion
intensities observed with TOFMS when the total ion concentration is high. 相似文献