共查询到20条相似文献,搜索用时 171 毫秒
1.
P. Haro-González I. R. Martin F. Lahoz S. González-Pérez N. E. Capuj D. Jaque 《Applied Physics A: Materials Science & Processing》2008,93(4):977-981
Localized desvitrifiation in strontium barium niobate glass doped with Er3+ under laser irradiation has been carried out. The samples of this study have been fabricated by the melt quenching method
and doped with 5% mol of Er3+. A 1.5-W cw Ar laser was focused on the sample to obtain desvitrifiation of the glass. Evidence of the changes induced by
the Ar laser has been observed through the analysis of the photoluminescence of the Er3+ ions. The transitions corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 have been studied to analyze structure changes. Microluminescence measurements have been carried out to spatially select
positions inside and outside the irradiated area. We have observed changes in the emission bands corresponding to these transitions.
The emission bands from Er3+ ions in the irradiated zone show a resolved structure while they are broadened outside that area. These changes in the optical
properties of the Er3+ ions indicate that the Ar-laser irradiation has produced a change in the local structure of the material. These results show
that a localized desvitrifiation has been produced after the laser action and the transition from glass to glass ceramic has
been completed. 相似文献
2.
M. Novotný J. Bulíř J. Lančok M. Jelínek Z. Zelinger 《Czechoslovak Journal of Physics》2006,56(4):381-388
Time- and spatially-resolved optical emission spectroscopy was performed to characterize the plasma produced in a hybrid magnetron-sputtering-laser
deposition system, which is used for TiC or SiC thin films preparation. A graphite target was ablated by a KrF excimer laser
(λ=248 nm,τ=20 ns) and either Ti or Si targets were used for DC magnetron sputtering in argon ambient. Spectra were measured in the range
250–850 nm. The evolution of the spectra with varying magnetron powers (0–100 W) and argon pressures (0.3–10 Pa) was studied.
Spectra of the plasmas produced by a) the magnetron alone, b) the ablation laser alone, and c) the magnetron and the ablation
laser together, were recorded. Spectra (a) were dominated by Ar atoms and Ar+ ions. Emission lines of Ti and Si were detected, when Ti target and Si target was used, respectively. Spectra (b) revealed
emission of C, C+, C2, Ar, Ar+. Spectra (c) showed presence of all previously mentioned species and further of Ti+ ions emission was detected.
The research was supported by Grant Agency of the Czech Republic No. 202/06/02161, GA ASCR project number A1010110/01 and
Institutional Research Plan AV CR No. AV0Z 10100522. 相似文献
3.
V. M. Gordienko I. M. Lachko A. A. Rusanov A. B. Savel’ev D. S. Uryupina R. V. Volkov 《Applied physics. B, Lasers and optics》2005,80(6):733-739
We present atomic, energy, and charge spectra of ions accelerated at the front surface of a silicon target irradiated by a high-contrast femtosecond laser pulse with an intensity of 3×1016 W/cm2, which is delayed with respect to a cleaning nanosecond laser pulse of 3-J/cm2 energy density. A tremendous increase in the number of fast silicon ions and a significant growth of their maximum charge in the case of the cleaned target from 5+ to 12+ have been observed. The main specific features of the atomic, energy, and charge spectra have been analyzed by means of one-dimensional hydrodynamic transient-ionization modeling. It is shown that fast highly charged silicon ions emerge from the hot plasma layer with a density a few times less than the solid one, and their charge distribution is not deteriorated during plasma expansion.This revised version was published online in August 2005 with a corrected cover date. 相似文献
4.
We describe a new technique to measure the UV/visible absorption spectrum of the ablated material during the laser pulse.
The technique utilizes the continuum emission from one laser produced plasma as a light source to measure the absorption properties
of a second laser produced plasma which is formed on a semi-transparent target with an array of 40 μm holes. A 6 ns, 1064
nm laser was used to ablate a Ag target and the plasma absorption was measured in the range 450–625 nm for a laser fluence
of 1 J cm−2. The total absorption cross-section is (0.5–1.5)×10−17 cm2 in the range 450–540 nm. By comparing the measured absorption with a calculation using the plasma spectroscopy code FLYCHK
it can be concluded that, in the wavelength region examined here, the absorption is mainly due to bound-bound transitions. 相似文献
5.
P.?Gibbon M.?Ma?ek U.?Teubner W.?Lu M.?Nicoul U.?Shymanovich A.?Tarasevitch P.?Zhou K.?Sokolowski-Tinten D.?von?der?Linde 《Applied Physics A: Materials Science & Processing》2009,96(1):23-31
Recent theoretical and numerical studies of laser-driven femtosecond K
α
sources are presented, aimed at understanding a recent experimental campaign to optimize emission from thin coating targets.
Particular attention is given to control over the laser–plasma interaction conditions defined by the interplay between a controlled
prepulse and the angle of incidence. It is found that the x-ray efficiency for poor-contrast laser systems in which a large
preplasma is suspected can be enhanced by using a near-normal incidence geometry even at high laser intensities. With high
laser contrast, similar efficiencies can be achieved by going to larger incidence angles, but only at the expense of larger
x-ray spot size. New developments in three-dimensional modelling are also reported with the goal of handling interactions
with geometrically complex targets and finite resistivity. 相似文献
6.
Jesús?álvarez-Ruiz Marien?López-Arias Rebeca?de?Nalda Margarita?Martín Andrés?Arregui Luis?Ba?ares 《Applied Physics A: Materials Science & Processing》2009,95(3):681-687
The formation of cationic clusters in the laser ablation of CdS targets has been investigated as a function of wavelength
and fluence by mass spectrometric analysis of the plume. Ablation was carried out at the laser wavelengths of 1064, 532, 355,
and 266 nm in order to scan the interaction regimes below and above the energy band gap of the material. In all cases, the
mass spectra showed stoichiometric Cd
n
S
n
+ and nonstoichiometric Cd
n
S
n−1+, Cd
n
S
n+1+, and Cd
n
S
n+2+ clusters up to 4900 amu. Cluster size distributions were well represented by a log-normal function, although larger relative
abundance for clusters with n=13, 16, 19, 34 was observed (magic numbers). The laser threshold fluence for cluster observation was strongly dependent on
wavelength, ranging from around 16 mJ/cm2 at 266 nm to more than 300 mJ/cm2 at 532 and 1064 nm. According to the behavior of the detected species as a function of fluence, two distinct families were
identified: the “light” family containing S2+ and Cd+ and the “heavy” clusterized family grouping Cd2+ and Cd
n
S
m
+. In terms of fluence, it has been determined that the best ratio for clusterization is achieved close to the threshold of
appearance of clusters at all wavelengths. At 1064, 532, and 355 nm, the production of “heavy” cations as a function of fluence
showed a maximum, indicating the participation of competitive effects, whereas saturation is observed at 266 nm. In terms
of relative production, the contribution of the “heavy” family to the total cation signal was significantly lower for 266 nm
than for the longer wavelengths. Irradiation at 355 nm in the fluence region of 200 mJ/cm2 has been identified as the optimum for the generation of large clusters in CdS. 相似文献
7.
J. Hoffman W. Mróz A. Prokopiuk Z. Szymanski 《Applied Physics A: Materials Science & Processing》2008,92(4):921-926
The plasma plume induced during ArF laser ablation of a graphite target is studied. Velocities of the plasma expansion front
are determined by the optical time of flight method. Mass center velocities of the emitting atoms and ions are constant and
amount to 1.7×104 and 3.8×104 m s−1, respectively. Higher velocities of ions result probably from their acceleration in electrostatic field created by electron
emission prior to ion emission. The emission spectroscopy of the plasma plume is used to determine the electron densities
and temperatures at various distances from the target. The electron density is determined from the Stark broadening of the
Ca II and Ca I lines. It reaches a maximum of ∼9.5×1023 m−3 30 ns from the beginning of the laser pulse at the distance of 1.2 mm from the target and next decreases to ∼1.2×1022 m−3 at the distance of 7.6 mm from the target. The electron temperature is determined from the ratio of intensities of ionic
and atomic lines. Close to the target the electron temperature of ∼30 kK is found but it decreases quickly to 11.5 kK 4 mm
from the target. 相似文献
8.
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
9.
A. Lorusso J. Krása L. Láska V. Nassisi L. Velardi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):473-476
In the last years the ion component of a laser-produced plasma has been considered and studied as an object to provide high-density
ion sources, which can be applied in many fields such as laser-induced implantation. In this work a KrF laser beam of 108 W/cm2 irradiance was focused onto single-crystalline Fe and single-crystalline Fe with 2% of Si targets and the characteristics
of both free expanding laser-produced plasmas were compared. The time-of-flight (TOF) method was applied to determine the
ion charge yield at various laser fluences and the ion angular spread. The analyses of TOF spectra showed a synergetic effect
of the silicon admixture in target material on the Fe ions production. Besides, this admixture was also responsible of the
increasing of the plasma temperature which corresponds in turn to the increasing of the average kinetic energy of the particles
as well as of the more collimated ion distribution. 相似文献
10.
A. Ferrier M. Velázquez J.-L. Doualan R. Moncorgé 《Applied physics. B, Lasers and optics》2009,95(2):287-291
This letter presents the optical and spectroscopic properties of a new low-energy phonon, moisture-resistant and non-linear
Pr3+:Tl3PbBr5 single crystal. Though only weakly doped with Pr3+ ions, centimetre-size and good-quality single crystals could be grown and analyzed. Absorption and emission spectra as well
as fluorescence kinetics were registered in the mid-infrared spectral domain. Strong luminescence at around 4–5.5 μm was observed
and assigned to the 3H5→3H4 transition of the Pr3+ ions. The high value of the resulting emission cross section associated with the long lifetime of the 3H5 emitting level indicates that this material could be a good candidate for the development of a broadly tunable mid-infrared
solid-state laser source. 相似文献
11.
Amin Abdolvand Robert W. Lloyd Marc J. J. Schmidt David J. Whitehead Zhu Liu Lin Li 《Applied Physics A: Materials Science & Processing》2009,95(2):447-452
We present results on the growth of highly organised, reproducible, periodic microstructure arrays on a stainless steel substrate
using multi-pulsed Nd:YAG (wavelength of 1064 nm, pulse duration of 7 ns, repetition rate of 25 kHz, beam quality factor of
M
2∼1.5) laser irradiation in standard atmospheric environment (room temperature and normal pressure) with laser spot diameter
of the target being ∼50 μm. The target surface was irradiated at laser fluence of ∼2.2 J/cm2 and intensity of ∼0.31×109 W/cm2, resulting in the controllable generation of arrays of microstructures with average periods ranging from ∼30 to ∼70 μm, depending
on the hatching overlap between the consecutive scans. The received tips of the structures were either below or at the level
of the original substrate surface, depending on the experimental conditions. The peculiarity of our work is on the utilised
approach for scanning the laser beam over the surface. A possible mechanism for the formation of the structures is proposed. 相似文献
12.
L.E. Batay A.A. Demidovich A.N. Kuzmin A.N. Titov M. Mond S. Kück 《Applied physics. B, Lasers and optics》2002,75(4-5):457-461
A new laser medium – Yb,Tm:KY(WO4)2 – for diode pumped solid state laser applications operating around 1.9 to 2.0 μm has been investigated and the main laser
characteristics are presented. Diode pumping at 981 nm and around 805 nm was realised. For 981-nm pumping, the excitation
occurs into Yb3+ ions followed by an energy transfer to Tm3+ions. A slope efficiency of 19% was realised. For pumping around 805 nm, the excitation occurs directly into the Tm3+ ions. Here a maximum slope efficiency of 52%, an optical efficiency of 40%, and output powers of more than 1 W were realised.
Using a birefringent quartz plate as an intracavity tuning element, the tunability of the Yb,Tm:KY(WO4)2 laser in the spectral range of 1.85–2.0 μm has been demonstrated. The possibility of laser operation in a microchip cavity
configuration for this material has also been shown.
Received: 12 March 2002 / Revised version: 20 May 2002 / Published online: 25 September 2002
RID="*"
ID="*"Corresponding author. Fax: +49-531/592-4116, E-mail: stefan.kueck@ptb.de 相似文献
13.
Intensity threshold in vacuum laser acceleration 总被引:1,自引:0,他引:1
J. Pang Y.K. Ho N. Cao L. Shao Y.J. Xie Z. Chen S.Y. Zhang 《Applied physics. B, Lasers and optics》2003,76(5):617-620
The dependence of the electron-energy gain on the on-axis laser intensity of a TEM00 light wave in vacuum, called the capture and acceleration scenario (CAS), has been studied. We found that there exists a
laser intensity threshold for the CAS scheme to work. The physical meaning of the intensity threshold is that, when the intensity
is strong enough, fast electrons injected into the Rayleigh zone where the phase velocity of the light wave is subluminous
can be accelerated until they catch up with the phase velocity before they slip out. Thereby these electrons can receive a
considerable amount of energy from the laser field. Analytical calculations based on this situation and simulation results
show similar features in that the intensity threshold value, (a0
T)2, is strongly dependent on the laser-beam width at focus, kw0. For example, kw0=40 corresponds to a0
T∼5, which is available by present laser systems. Also, it has been proved that the maximal electron-energy gain in the CAS
regime is linearly proportional to the laser intensity as well as to kw0.
Received: 20 January 2003 / Revised version: 6 March 2003 / Published online: 23 May 2003
RID="*"
ID="*"Corresponding author. Fax: +86-21/6564-3815, E-mail: hoyk@fudan.ac.cn 相似文献
14.
B. A. Zon A. S. Kornev E. B. Tulenko 《Journal of Experimental and Theoretical Physics》2010,111(6):921-935
Some of the many-body effects in the formation of multiply charged ions in a laser field have been taken into account: inelastic
tunneling, collective tunneling, and magnetic moment projection relaxation of the atomic core. Strong fields with an intensity
exceeding 1017 W cm−2 are considered when the magnetic component of the laser field acts on the free motion of a photoelectron; therefore, the
formation of multiply charged ions through rescattering becomes unlikely. Numerical calculations have been performed for Ar9+ … Ar13+, Kr19+ … Kr23+, Rb10+, and Rb11+ ions. A significant contribution of collective tunneling, which was not observed in weaker fields investigated previously,
has been revealed. Allowance for collective tunneling is shown to reduce the intensity leading to saturation by more than
10%. In this case, the yield of multiply charged Rb ions changes by an order of magnitude, while the yield of multiply charged
Ar and Kr ions changes by more than a factor of 2. Comparison with experimental data on the formation of argon ions under
the action of a linearly polarized laser pulse is made. 相似文献
15.
D. Margarone L. Láska S. Gammino E. Krouský M. Pfeifer M. Rosiñski J. Skála A. Velyhan 《Applied Surface Science》2008,254(9):2797-2803
Long pulse laser shots of the PALS iodine laser in Prague have been used to obtain metal target ablation at various experimental conditions. Attention is paid mainly to the dependencies of the crater diameter on the position of minimum laser-focus spot with regard to the target surface, by using different laser wavelengths and laser energies. Not only a single one, but two minima, independently of the wavelength, of the target irradiation angle and of the target material, were recorded. Significant asymmetries, ascribed to the non-linear effects of intense laser beam with pre-formed plasma, were found, too. Estimations of ejected mass per laser pulse are reported and used to calculate the efficiency of laser-driven loading. Results on metal target ablation and crater formation at high intensities (from 2 × 1013 to 3 × 1016 W/cm2) are presented and compared. Crater depth, crater diameter and etching yield are reported versus the laser energy, in order to evaluate the ablation threshold fluence. 相似文献
16.
S. Canulescu T. Lippert A. Wokaun 《Applied Physics A: Materials Science & Processing》2008,93(3):771-778
The mass distributions of the species generated by laser ablation from a La0.6Ca0.4MnO3 target using laser irradiation wavelengths of 193 nm, 266 nm and 308 nm have been investigated with and without a synchronized
gas pulse of N2O. The kinetic energies of the species are measured using an electrostatic deflection energy analyzer, while the mass distributions
of the species were analyzed with a quadrupole mass filter.
In vacuum (pressure 10−7 mbar), the ablation plume consists of metal atoms and ions such as La, Ca, Mn, O, LaO, as well as multiatomic species, e.g.
LaMnO+. The LaO+ diatomic species are by far the most intense diatomic species in the plume, while CaO and MnO are only detected in small
amounts.
The interaction of a reactive N2O gas pulse with the ablation plume leads to an increase in plume reactivity, which is desired when thin manganite films are
grown, in order to incorporate the necessary amount of oxygen into the film. The N2O gas pulse appears to have a significant influence on the oxidation of the Mn species in the plume, and on the creation of
negative ions, such as LaO−,O− and O2−. 相似文献
17.
M.?Silies H.?Witte S.?Linden J.?Kutzner I.?Uschmann E.?F?rster H.?Zacharias 《Applied Physics A: Materials Science & Processing》2009,96(1):59-67
The interaction of ultrashort laser pulses with solid state targets is studied concerning the production of short X-ray pulses
with photon energies up to about 10 keV. The influence of various parameters such as pulse energy, repetition rate of the
laser system, focusing conditions, the application of prepulses, and the chirp of the laser pulses on the efficiency of this
highly nonlinear process is examined. In order to increase the X-ray flux, the laser pulse energy is increased by a 2nd multipass
amplifier from 750 μJ to 5 mJ. By applying up to 4 mJ of the pulse energy a X-ray flux of 4×1010 Fe K
α
photons/s or 2.75×1010 Cu K
α
photons/s are generated. The energy conversion efficiency is therefore calculated to η
Fe≈1.4×10−5 and η
Cu≈1.0×10−5. The X-ray source size is determined to 15×25 μm2. By focusing the produced X-rays using a toroidally bent crystal a quasi-monochromatic X-ray point source with a diameter
of 56 μm×70μm is produced containing ≈104 Fe K
α1 photons/s which permits the investigation of lattice dynamics on a picosecond or even sub-picosecond time scale. The lattice
movement of a GaAs(111) crystal is shown as a typical application. 相似文献
18.
P.E. Dyer S.M. Maswadi C.D. Walton 《Applied Physics A: Materials Science & Processing》2003,76(5):817-822
We report an investigation of the ablation of NaCl crystals at the 157-nm wavelength of the F2 laser where there is very strong excitonic absorption. Probe-beam deflection and etch-rate measurements show that the interaction
is characterised by a low ablation threshold (∼80 mJ cm-2) and a capability for controllable material removal at the nanometer level. Scanning electron microscopy of the exposed surfaces
show this to be microscopically smooth but with fine cracks present. It is demonstrated that micron-scale features can be
formed in NaCl using 157-nm laser ablation, a result attributed to the strongly localised optical and thermal nature of the
interaction. The results are discussed within the framework of a thermal vaporisation model.
Received: 29 May 2002 / Accepted: 17 July 2002 / Published online: 4 November 2002
RID="*"
ID="*"Corresponding author. Fax: +44-1482/465606, E-mail: p.e.dyer@hull.ac.uk 相似文献
19.
We present a numerical model of Er3+–Tm3+–Pr3+-co-doped fiber amplifier pumped with 980 nm laser for the first time, to the best of our knowledge. The rate and power propagation
equations are solved numerically to analyze the effects of the pump power and active ion concentrations on the gains at 1310,
1470, 1530, 1600, 1650 nm windows. The results show that with pump power of 200 mW and when Pr3+, Tm3+, Er3+ concentrations are around 2.0×1024, 3.0×1024, 1.5×1024 (ions/m3), respectively, the signals at 1470, 1530, 1600 nm may be nearly equally amplified with gain of 11–12.0 dB in the active
fiber with length of 11.0 m, and the signals at 1310, 1470 and 1600 nm windows may be nearly equally amplified with gain of
12.0 dB in the active gain medium with length of 15.0 m. With pump power of 300 mW, the signals at 1470, 1530, 1600 nm may
be nearly equally amplified with a gain of 16.0 dB in the active medium with a length of 15.0 m. 相似文献
20.
L. R. P. Kassab F. A. Bomfim J. R. Martinelli N. U. Wetter J. J. Neto Cid B. de Araújo 《Applied physics. B, Lasers and optics》2009,94(2):239-242
We report the infrared-to-visible frequency upconversion in Er3+–Yb3+-codoped PbO-GeO2 glass containing silver nanoparticles (NPs). The optical excitation is made with a laser at 980 nm in resonance with the
2F5/2→2F7/2 transition of Yb3+ ions. Intense emission bands centered at 525, 550, and 662 nm were observed corresponding to Er3+ transitions. The simultaneous influence of the Yb3+→Er3+ energy transfer and the contribution of the intensified local field effect due to the silver NPs give origin to the enhancement
of the whole frequency upconversion spectra. 相似文献