共查询到20条相似文献,搜索用时 437 毫秒
1.
S.I. Dolgaev S.V. Lavrishev A.A. Lyalin A.V. Simakin V.V. Voronov G.A. Shafeev 《Applied Physics A: Materials Science & Processing》2001,73(2):177-181
The formation and development of the large-scale periodic structures on a single crystal Si surface are studied upon its evaporation
by pulsed radiation of a copper vapor laser (wavelength of 510.6 nm, pulse duration of 20 ns). The development of structures
occurs at a high number of laser shots (∼104) at laser fluence of 1–2 J/cm2 below optical breakdown in a wide pressure range of surrounding atmosphere from 1 to 105 Pa. The structures are cones with angles of 25, which grow towards the laser beam and protrude above the initial surface
for 20–30 μm. It is suggested that the spatial period of the structures (10–20 μm) is determined by the capillary waves period
on the molten surface. The X-ray diffractometry reveals that the modified area of the Si substrate has a polycrystalline structure
and consists of Si nanoparticles with a size of 40–70 nm, depending on the pressure of surrounding gas. Similar structures
are also observed on Ge and Ti.
Received: 12 February 2000 / Accepted: 28 March 2000 / Published online: 20 June 2001 相似文献
2.
Robert Lloyd Amin Abdolvand Marc Schmidt Philip Crouse David Whitehead Zhu Liu Lin Li 《Applied Physics A: Materials Science & Processing》2008,93(1):117-122
Utilising a Nd:YVO4 laser (wavelength of 532 nm, pulse duration of 8 ns, repetition rate of 30 kHz) and a Nd:YAG laser (wavelength of 1064 nm,
pulse duration of 7 ns, repetition rate of 25 kHz), it was found that during the pulsed laser ablation of metal targets, such
as stainless steel, periodic nodular microstructures (microcones) with average periods ranging from ∼30 to ∼50 μm were formed.
This period depends on the number of accumulated laser pulses and is independent of the laser wavelength. It was found that
the formation of microcones could occur after as little as 1500 pulses/spot (a lower number than previously reported) are
fired onto a target surface location at laser fluence of ∼12 J/cm2, intensity of ∼1.5 GW/cm2. The initial feedback mechanism required for the formation of structures is attributed to the hydrodynamic instabilities
of the melt. In addition to this, it has been shown that the structures grow along the optical axis of the incoming laser
radiation. We demonstrate that highly regular structures can be produced at various angles, something not satisfactorily presented
on metallic surfaces previously. The affecting factors such as incident angle of the laser beam and the structures that can
be formed when varying the manner in which the laser beam is scanned over the target surface have also been investigated. 相似文献
3.
Hirofumi Hidai David J. Hwang Costas P. Grigoropoulos 《Applied Physics A: Materials Science & Processing》2008,93(2):443-445
We demonstrate a new fiber growth mechanism in a photocurable resin by ultrafast laser illumination. A high-repetition rate
(∼1 MHz) ultrafast laser beam at the wavelength of ∼523 nm was focused into an ultraviolet photocurable resin to trigger two-photon
photopolymerization process. Time-resolved shadowgraphs and scattered light imaging revealed that the curing commenced in
the neighborhood of the geometric focal point of the laser beam and that the fiber growth progressed mostly towards the laser source. The cured fiber was thinner and longer than the profile of the focused laser beam, facilitated by nonlinear
propagation and absorption of the ultra-fast laser beam. The achieved aspect ratio of the fiber was higher than 180 with ∼10 μm
mean diameter, and the average growth rate was up to ∼2 mm/s. 相似文献
4.
N. G. Semaltianos W. Perrie P. French M. Sharp G. Dearden S. Logothetidis K. G. Watkins 《Applied Physics A: Materials Science & Processing》2009,94(4):999-1009
Femtosecond laser (180 fs, 775 nm, 1 kHz) ablation characteristics of the nickel-based superalloy C263 are investigated. The
single pulse ablation threshold is measured to be 0.26±0.03 J/cm2 and the incubation parameter ξ=0.72±0.03 by also measuring the dependence of ablation threshold on the number of laser pulses.
The ablation rate exhibits two logarithmic dependencies on fluence corresponding to ablation determined by the optical penetration
depth at fluences below ∼5 J/cm2 (for single pulse) and by the electron thermal diffusion length above that fluence. The central surface morphology of ablated
craters (dimples) with laser fluence and number of laser pulses shows the development of several kinds of periodic structures
(ripples) with different periodicities as well as the formation of resolidified material and holes at the centre of the ablated
crater at high fluences. The debris produced during ablation consists of crystalline C263 oxidized nanoparticles with diameters
of ∼2–20 nm (for F=9.6 J/cm2). The mechanisms involved in femtosecond laser microprocessing of the superalloy C263 as well as in the synthesis of C263
nanoparticles are elucidated and discussed in terms of the properties of the material. 相似文献
5.
Seong Shan Yap Alesya Viktorovna Salomatova Cécile Ladam ?ystein Dahl Turid Worren Reenaas 《Applied Physics A: Materials Science & Processing》2010,101(4):765-770
A KrF laser was used to ablate a polycrystalline Si target for deposition of Si on MgO and GaAs substrates at room temperature.
The deposition was performed in 10−8 mbar, with two types of laser beams: a homogeneous beam being imaged onto the target (2.9 J/cm2), and a non-homogeneous which is nearly focused (2 J/cm2, 6.5 J/cm2). In both cases, the beam was scanned over an area of 1 cm2. For the homogenous beam, we observed only a limited number of droplets (<0.1 μm). A high number of micron-sized (<5 μm)
droplets were observed on the film by the higher fluence nonhomogeneous laser beam. Raman spectroscopy showed that the micron-sized
droplets are crystalline while the film is amorphous. The generation of the large droplets is most likely related to the cone
structures formed on the ablated target. We also compared cone formation on a polycrystalline Si target and a single crystalline
Si wafer, using multiple laser pulses onto a single spot. 相似文献
6.
Dattatray J. Late Vindhyesh R. Singh Sucharita Sinha Mahendra A. More K. Dasgupta Dilip S. Joag 《Applied Physics A: Materials Science & Processing》2009,97(4):905-909
Micro/nano structures have been obtained by laser surface treatment on sintered LaB6 pellets employing a picosecond pulsed Nd:YAG laser at a pressure of ∼1×10−3 mbar. The X-ray diffraction pattern of the laser treated pellet shows a set of well defined diffraction peaks, indexed to
the cubic phase of LaB6 only. The scanning electron microscope studies reveal formation of micro and nano structures upon laser treatment and the
resultant surface morphology is found to be strongly influenced by the laser fluence. Field electron emission studies made
on the LaB6 pellet, treated with optimized laser fluence, have been performed in a planar diode configuration under ultra high vacuum
conditions. The threshold field required to draw an emission current density of ∼10 μA/cm2 has been found to be ∼2.3 V/μm and a current density of ∼530 μA/cm2 has been drawn at an applied field of 5.2 V/μm. The Fowler-Nordheim plot is found to be linear in accordance with the quantum
mechanical tunneling phenomenon, confirming the metallic nature of the emitter. The emission current at the pre-set value
∼10 μA shows very good stability over a period of more than 3 hours. The present results emphasize the effectiveness of a
picosecond laser treatment towards fabrication of a nano metric LaB6 emitter for high current density applications. 相似文献
7.
J. Cousin W. Chen D. Bigourd M. Fourmentin S. Kassi 《Applied physics. B, Lasers and optics》2009,97(4):919-929
We report on the development of a field deployable compact laser instrument tunable over ∼232 cm−1 from 3.16 to 3.41 μm (2932.5–3164.5 cm−1) for chemical species monitoring at the ppb-level. The laser instrument is based on widely tunable continuous-wave difference-frequency
generation (DFG), pumped by two telecom-grade fiber lasers. DFG power of ∼0.3 mW near 3.3 μm with a spectral purity of ∼3.3
MHz was achieved by using moderate pumping powers: 408 mW at 1062 nm and 636 mW at 1570 nm. Spectroscopic performance of the
developed DFG-based instrument was evaluated with direct absorption spectra of ethylene at 3.23 μm (∼3094.31 cm−1). Absorption spectra of vapor-phase benzene near 3.28 μm (∼3043.82 cm−1) were recorded with Doppler-limited resolution. Line intensities of the most intense absorption lines of the ν
12 band near 3043.8 cm−1 were determined to support development of sensitive mid-infrared trace gas detection of benzene vapor in the atmosphere.
Detection of benzene vapor in air at different concentration levels has been performed for the first time using multi-pass
cell enhanced direct absorption spectroscopy at ∼3.28 μm with a minimum detectable concentration of 50 ppb (1σ). 相似文献
8.
V. P. Rotshtein Yu. F. Ivanov A. B. Markov D. I. Proskurovskii K. V. Oskomov V. V. Uglov S. N. Dub Y. Pauleau I. A. Shulepov 《Russian Physics Journal》2005,48(12):1221-1228
The surface topography, chemical composition, microstructure, nanohardness, and tribological characteristics of a Cu (film,
512 nm)-stainless steel 316 (substrate) system subjected to pulsed melting by a low-energy (20–30 keV), high-current electron
beam (2–3 μs, 2–10 J/cm2) were investigated. The film was deposited by sputtering a Cu target in the plasma of a microwave discharge in argon. To
prevent local exfoliation of the film due to cratering, the substrate was multiply pre-irradiated with 8–10 J/cm2. On single irradiation, the bulk of the film survived, and a diffusion layer containing the film and substrate components
was formed at the interface. The thickness of this layer was 120–170 nm irrespective of the energy density. The diffusion
layer consisted of subgrains of γ-Fe solid solution and nanosized particles of copper. In the surface layer of thickness 0.5–1 μm, which included the copper
film quenched from melt and the diffusion layer, the nanohardness and the wear resistance nonmonotonicly varied with energy
density, reaching, respectively, a maximum and a minimum in the range 4.3–6.3 J/cm2. As the number of pulsed melting cycles was increased to five in the same energy density range, there occurred mixing of
the film-substrate system and a surface layer of thickness ∼2 μm was formed which contained ∼20 at. % copper. Displacement
of the excess copper during crystallization resulted in the formation of two-phase nanocrystal interlayers separating the
γ-phase grains.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 6–13, December, 2005. 相似文献
9.
Radek Zeipl Jarmila Walachová Martin Pavelka Miroslav Jelínek Václav Studnička Tomáš Kocourek 《Applied Physics A: Materials Science & Processing》2008,93(3):663-667
Room temperature conductivity and the Seebeck coefficient of thin layers prepared by laser ablation from Bi2Te3 target were explored. The power factor was calculated for samples prepared at substrate temperature of 360°C with the density
of the laser beam 5 J cm−2 and at substrate temperature of 410°C with the density of the laser beam 2 J cm−2 during the deposition. Oscillations of the conductivity and the power factor with the layer thickness were observed at room
temperature. The oscillations of conductivity were also verified at the temperature of 77 K. The period of oscillations depends
on the preparation conditions. This behavior has been theoretically explained by the quantum size effect in the layers containing
different phases and in addition, it was demonstrated by the X-ray Diffraction measurement.
The behavior of the power factor of the layers is compared to the behavior of the figure of merit of the layers published
earlier. 相似文献
10.
W.M. Shu Y. Kawakubo M.F. Nishi 《Applied Physics A: Materials Science & Processing》2003,76(3):421-425
Recovery of tritium from co-deposited layers formed in deuterium–tritium plasma operations of the TFTR (Tokamak Fusion Test
Reactor) was investigated by the use of an ArF excimer laser operating at the wavelength of 193 nm. At the laser energy density
of 0.1 J/cm2, a transient spike of the tritium-release rate was observed at initial irradiation. Hydrogen isotopes were released in the
form of hydrogen-isotope molecules during the laser irradiation in vacuum, suggesting that tritium can be recovered readily
from the released gases. In a second experiment, hydrogen (tritium) recovery from the co-deposited layers on JT-60 tiles that
had experienced hydrogen-plasma operations was investigated by laser ablation with a focused beam of the excimer laser. The
removal rate of the co-deposited layers was quite low when the laser energy density was smaller than the ablation threshold
(1.0 J/cm2), but reached 1.1 μm/pulse at the laser energy density of 7.6 J/cm2. The effective absorption coefficient in the co-deposited layers at the laser wavelength was determined to be 1.9 μm-1. The temperature of the surface during the irradiation at the laser energy density of 0.5 J/cm2 was measured on the basis of Planck’s law of radiation, and the maximum temperature during the irradiation decreased from
3570 K at the initial irradiation to 2550 K at the 1000th pulse of the irradiation.
Received: 5 August 2002 / Accepted: 7 August 2002 / Published online: 28 October 2002
RID="*"
ID="*"Corresponding author. Fax: +81-29/2825917, E-mail: shu@tpl.tokai.jaeri.go.jp 相似文献
11.
V. A. Andronov S. A. Bel’kov A. V. Bessarab I. N. Voronich S. G. Garanin A. A. Gorbunov V. N. Derkach G. V. Dolgoleva A. I. Zaretskii V. M. Izgorodin B. N. Ilyushechkin G. A. Kirillov G. G. Kochemasov Yu. V. Kuratov V. I. Lazarchuk V. A. Lebedev V. M. Murugov L. S. Mkhitar’yan A. V. Okutin S. I. Petrov A. V. Pinegin N. N. Rukavishnikov A. N. Razin A. V. Ryadov A. V. Senik N. A. Suslov S. A. Sukharev V. A. Tokarev 《Journal of Experimental and Theoretical Physics》1997,84(3):485-488
The results of the first experiments devised to investigate the mixing of thin layers of Al and Au during the laser acceleration
of flat three-layer targets of Si (5 μm), Al (2 μm), and Au (0.05–0.26 μm) by radiation converted to the second harmonic from the Iskra-4 iodine laser with an intensity of 4×1013−7×1013 W/cm2 (τ
0.5∼1 ns), which acts on the Si side of the target. A method for detecting the occurrence of mixing is developed. It is established
that under the experimental conditions the thickness of the mixing region is at least ∼0.15 μm. The results of a theoretical analysis of the evolution of the disturbances leading to mixing are presented.
Zh. éksp. Teor. Fiz. 111, 882–888 (March 1997)
Deceased. 相似文献
12.
H. Shu S.-Z. Fu X.-G. Huang M.-X. Ma J. Wu J.-J. Ye J.-H. He Y. Gu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):367-370
Using the ninth laser beam (converted to 2ω) of
“Shenguang-II” laser facility and the beam smoothing technology of
lens-array [Appl. Opt. 25, 377 (1986); Phys. Plasmas. 9, 3201 (1995)],
a shock wave with 700 μm (the root-mean-square of
shock breakout time (RMS) RMS ≈ 6.32 ps) flat top was created. An Al-Al
four-step target was designed to do research on shock wave stability in an
Al target. And the shock stability experiment with the Al-Al four-step
target indicated that the shock wave steadily propagated in the Al target of
thickness of about 20–45 μm under the power density of ~ 1.0×1014 W/cm2. 相似文献
13.
P. Zhang H. Qi X. Zhang Q. Zhao Y. Tian D. Yu 《Applied Physics A: Materials Science & Processing》2006,84(1-2):165-169
Novel lotiform ZnO nanostructures were synthesized on silicon substrate via simple thermal evaporation. The average diameter of the ZnO nanostructures is ∼1.5 μm. The lotiform-like ZnO structures were formed by nanorods arrays with the average diameter of 70 nm. The as-grown lotiform ZnO nanostructures have excellent field-emission properties such as the low turn-on field of 3.4 V/μm, and very high emission current density of 12.4 mA/cm2 at the field of 9.6 V/μm. These features make the lotiform-like ZnO nanostructures competitive candidates for field-emission-based displays. PACS 61.46.-w; 61.82.Rx; 78.67.-n; 73.63.Bd; 74.78.Na 相似文献
14.
A c-cut Tm:YAP laser which operated at 1.94 or 1.99 μm is reported in detail. The maximum output power was 20.4 and 19.8 W at
the wavelength around 1.99 and 1.94 μm, corresponding to the slope efficiency of 34.3 and 31.5%, respectively. For 1.94 μm
operation, with an F-P etalon inserted in the cavity, the output central wavelength was stable around 1.94 μm with about 0.15
nm linewidth. The beam quality factor M
2 was measured to be ∼1.8 for 1.99 μm and ∼1.9 for 1.94 μm. 相似文献
15.
D. Batani R. Benocci R. Dezulian R. Redaelli F. Canova H. Stabile G. Lucchini V. Malka J. Faure M. Koenig E. Krousky K. Masek M. Pfeifer J. Skala R. Dudzak J. Limpouch V. Tikhoncuk P. Nicolai 《The European physical journal. Special topics》2009,175(1):65-70
Smoothing of laser beam non-uniformities using gas jets has been studied. The experiment has been performed with the PALS
laser working at 0.44 μm with an intensity of about 1015 W/cm2. The laser beam has been split in two by a prism thus creating an artificial large-scale non-uniformity (≈90 μm). We recorded
time resolved and static images of laser-gas jet interaction with and without an Al target. Multi 1D and 2D simulations show
that such interaction acts redistributing the over-intensities over larger surface. This effect has to be attributed to ionization
processes with consequent laser beam refraction. Results show that Argon gas jet produces a strong refraction of the laser
beam thus strongly reducing the initial two spots separation. 相似文献
16.
F. Beinhorn J. Ihlemann K. Luther J. Troe 《Applied Physics A: Materials Science & Processing》1999,68(6):709-713
Micro-lenses with well-defined optical parameters are generated on polymethylmethacrylate (PMMA) substrates doped with diphenyltriazene
(DPT) by controlled use of a swelling effect generated under conditions of subablative excimer laser illumination. The surface
profiles depend on the laser spot size and energy density. A sensitively balanced combination of matrix softening, substrate
volume expansion due to photochemical nitrogen release, and surface tension is responsible for the final shape of the lenses.
Complete arrays of identical lenses with 15 μm diameters and a focal length of 30 μm are produced by irradiation of (0.25 wt. %)
DPT-PMMA with a single laser pulse at a wavelength of 308 nm and a fluence of 3 J/cm2. It is shown experimentally and theoretically that appropriate volume expansion is possible without introducing internal
light scattering due to the formation of small bubbles.
Received: 7 April 1999 / Accepted: 8 April 1999 / Published online: 5 May 1999 相似文献
17.
The dependence of the ablation rate of aluminium on the fluence of nanosecond laser pulses with wavelengths of 532 nm and
respectively 1064 nm is investigated in atmospheric air. The fluence of the pulses is varied by changing the diameter of the
irradiated area at the target surface, and the wavelength is varied by using the fundamental and the second harmonic of a
Q-switched Nd-YAG laser system. The results indicate an approximately logarithmic increase of the ablation rate with the fluence
for ablation rates smaller than ∼6 μm/pulse at 532 nm, and 0.3 μm/pulse at 1064 nm wavelength. The significantly smaller ablation rate at 1064 nm is due to the small optical absorptivity,
the strong oxidation of the aluminium target, and to the strong attenuation of the pulses into the plasma plume at this wavelength.
A jump of the ablation rate is observed at the fluence threshold value, which is ∼50 J/cm2 for the second harmonic, and ∼15 J/cm2 for the fundamental pulses. Further increasing the fluence leads to a steep increase of the ablation rate at both wavelengths,
the increase of the ablation rate being approximately exponential in the case of visible pulses. The jump of the ablation
rate at the threshold fluence value is due to the transition from a normal vaporization regime to a phase explosion regime,
and to the change of the dimensionality of the hydrodynamics of the plasma-plume.
相似文献
18.
J. S. Yu S. Slivken A. Evans M. Razeghi 《Applied Physics A: Materials Science & Processing》2008,93(2):405-408
High-temperature, high-power, and continuous-wave (CW) operation of quantum-cascade lasers with 35 active/injector stages
at λ∼8.85 μm above room temperature is achieved without using a buried heterostructure. At this long wavelength, the use of a
wider ridge waveguide in an epilayer-down bonding scheme leads to a superior performance of the laser. For a high-reflectivity-coated
21 μm×3 mm laser, the output power of 237 mW and the threshold current density of 1.44 kA/cm2 at 298 K under CW mode are obtained with a maximum wall-plug efficiency of 1.7%. Further improvements were observed by using
a 4-mm-long cavity. The device exhibits 294 mW of output power at 298 K and it operates at a high temperature, even up to
358 K (85°C). The full widths at half-maximum of the laser beam in CW operation for the parallel and the perpendicular far-field
patterns are 25°and 63°, respectively. 相似文献
19.
We have theoretically investigated the thermal characteristics of double-channel ridge–waveguide InGaAs/InAlAs/InP quantum
cascade lasers (QCLs) using a two-dimensional heat dissipation model. The temperature distribution, heat flow, and thermal
conductance (G
th) of QCLs were obtained through the thermal simulation. A thick electroplated Au around the laser ridges helps to improve
the heat dissipation from devices, being good enough to substitute the buried heterostructure (BH) by InP regrowth for epilayer-up
bonded lasers. The effects of the device geometry (i.e., ridge width and cavity length) on the G
th of QCLs were investigated. With 5 μm thick electroplated Au, the G
th is increased with the decrease of ridge width, indicating an improvement from G
th=177 W/K⋅cm2 at W=40 μm to G
th=301 W/K⋅cm2 at W=9 μm for 2 mm long lasers. For the 9 μm×2 mm epilayer-down bonded laser with 5 μm thick electroplated Au, the use of InP
contact layer leads to a further improvement of 13% in G
th, and it was totally raised by 45% corresponding to 436 W/K⋅cm2 compared to the epilayer-up bonded laser with InGaAs contact layer. It is found that the epilayer-down bonded 9 μm wide BH
laser with InP contact layer leads to the highest G
th=449 W/K⋅cm2. The theoretical results were also compared with available obtained experimentally data. 相似文献
20.
A.R. Präg F. Löwenthal R. Tommasini J.E. Balmer 《Applied physics. B, Lasers and optics》1998,66(5):561-566
2 . By using a 0.7% prepulse that precedes the main pulse by 5 ns and applying a total pump energy of 100 J or less, the J=0-1
lasing is at least one order of magnitude higher than the non-lasing background. For the 32.6-nm line of Ti, the 25.5-nm line
of Fe, and the 23.1-nm line of Ni, gain coefficients of (±) 4.20.4cm-1, (±) 3.90.3cm-1, and (±) 3.60.6cm-1, respectively, were measured for 2.4-cm-long curved targets, resulting in gain–length products of ∼10. Angle-resolved spectra
indicate a beam divergence of 3 mrad (FWHM), typically. The space-resolved spectra show that the J=0-1 lasing lines are emitted
from an approximately 60-μm-wide (FWHM) plasma region, whereas the nearby continuum emission is produced in a considerably
broader plasma region of ∼250 μm. Lasing at 25.5 nm in neon-like iron was observed at a pump power as low as 180 GW (∼9 TW/cm2), with, however, considerable shot-to-shot scatter in the absolute laser output.
Received: 5 September 1997/Revised version: 10 November 1997 相似文献