共查询到20条相似文献,搜索用时 31 毫秒
1.
A miniaturized, high repetition rate, picosecond all solid state photo-induced distributed feedback (DFB) polymer-dye laser
is described by applying a passively Q-switched and frequency-doubled Cr4+:Nd3+:YAG-microchip laser (pulse width Δτ=540 ps, repetition rate ν=3 kHz, pump energy Epump=0.15 μJ) as a pump source. A poly-methylmethacrylate film doped with rhodamine B dye serves as active medium. The DFB-laser
pulses are temporally and spectrally characterized, and the stability of the thin polymer/dye film at high repetition rates
is analyzed. The shortest DFB-laser pulses obtained have a duration of 11 ps. After the emission of 350000 pulses the intensity
of the DFB-laser output has decreased by a factor of two and the pulse duration has increased by a factor of 1.2. For single
DFB-laser pulses of 20-ps duration the spectral bandwidth is measured to be Δλ=0.03 nm, which is only 0.005 nm above the calculated
Fourier limit assuming a Gaussian profile for the temporal shape of the pulses. Coarse wavelength tuning of the DFB laser
between 590 and 619 nm is done by turning the prism. Additionally, a fine tuning of the DFB-polymer-laser wavelength is achieved
by changing the temperature of the polymer/dye layer (=-0.05 nm/°C) in the range from 20 to 40 °C.
Received: 1 March 2001 / Revised version: 23 May 2001 / Published online: 18 July 2001 相似文献
2.
F. Kokai M. Taniwaki M. Ishihara Y. Koga 《Applied Physics A: Materials Science & Processing》2002,74(4):533-536
We deposited amorphous thin films of boron carbide by pulsed laser deposition using a B4C target at room temperature. As the laser fluence increased from 1 to 3 J/cm2, the number of 0.25–5 μm particulates embedded in the films decreased, and the B/C atomic ratio of the films increased from
1.8 to 3.2. The arrival of melt droplets, atoms, and small molecular species depending on laser fluence appeared to be involved
in the film formation. In addition, with increasing fluence the nanoindentation hardness of the films increased from 14 to
32 GPa. We believe that the dominant factor in the observed increase in the films’ hardness is the arrival of highly energetic
ions and atoms that results in the formation of denser films.
Received: 23 March 2001 / Accepted: 1 July 2001 / Published online: 2 October 2001 相似文献
3.
H. Daido S. Yamagami M. Suzuki H. Azuma I.W. Choi H. Fiedorowicz 《Applied physics. B, Lasers and optics》2001,72(3):385-387
We have measured low-energy ion emission from a gas-puff laser-plasma X-ray source. The ions may cause the degradation of
the condenser mirror of the extreme ultra-violet projection lithography system. A 0.7 J in 8 ns Nd:YAG laser at 1.06 μm was
focused onto the xenon gas-puff target with an intensity of ∼1012 W/cm2. The silicon (111) plates, placed at a distance of 32 mm from the laser-interaction region, were exposed with the xenon ions.
The average ion energy was measured to be less than 50 eV with a Faraday-cup detector placed close to the silicon plates.
The xenon deposition occurred in the silicon plates with a depth of less than 40 nm. The deposition density was measured with
a quadrupole secondary ion mass spectrometer to be 1021 /cm3 after 1500 laser shots. The energy-conversion efficiency from the laser energy into the ions is ∼0.1%/4 π sr/shot. For the
lithography system, if we can remove such ion bombardment completely using novel techniques such as electro-magnetic devices
or gas flow curtain techniques, the lifetime of the condenser mirror will be extended significantly.
Received: 20 November 2000 / Published online: 9 February 2001 相似文献
4.
We demonstrate an optical limiter for ultra-short (∼100-fs) laser pulses. The device has a dynamic range (= damage energy/onset-of-limiting
energy) of more than 10000 and an onset-of-limiting energy of only ∼10 nJ. The output-pulse energy is kept below 1.3 μJ. The
limiting mechanism is based on two-photon absorption and refractive nonlinearities in a 20-mm piece of ZnSe. We discuss the
importance of the different nonlinearities, damage issues, and guidelines for the construction of the device.
Received: 20 December 2001 / Revised version: 25 March 2002 / Published online: 8 May 2002 相似文献
5.
M. Wieland T. Wilhein M. Faubel Ch. Ellert M. Schmidt O. Sublemontier 《Applied physics. B, Lasers and optics》2001,72(5):591-597
A liquid jet of either nitrogen or argon of 20 μm diameter was exposed to intense laser fields with pulse durations between
70 fs and 250 ps, leading to intensities of 1016 W cm-2 and 1013 W cm-2, respectively. The emission of extreme UV light and soft X-rays shows the characteristic lines of hydrogen-like nitrogen
and carbon-like argon. For nitrogen the emitted photon flux at 250 ps was about two orders of magnitude higher than for 70 fs
pulses. A weak dependence on the laser polarization with respect to the liquid jet axis was found. The kinetic energy of the
emitted ions easily exceeded 100 keV for nitrogen and 200 keV for argon for a pulse duration close to 2 ps.
Received: 21 August 2000 / Revised version: 20 December 2000 / Published online: 22 March 2001 相似文献
6.
R. Lopez R. Ruiz R.F. Haglund Jr. L.C. Feldman 《Applied Physics A: Materials Science & Processing》2002,74(2):307-310
We describe the fabrication by room-temperature pulsed laser deposition of a transparent conductor comprising alternating
layers of silver and aluminum oxide, forming a metallo-dielectric filter. Transmittances of 0.7 over specific wavelength bands
were achieved with resistivities as low as 6.0×10-6 Ω cm, almost two orders of magnitude lower than that of the best single-substrate thin films, such as indium tin oxide. The
resistivity can be predicted without adjustable parameters and designed using a simple parallel-circuit model; the optical
properties are well described by standard matrix transmission calculations. This demonstrates that pulsed laser deposition
may be used to fabricate prototypes of high-quality transparent conductors with predictable properties for conducting windows
where low-temperature deposition is critical, as in organic light-emitting diodes and for non-linear optical films.
Received: 10 June 2001 / Accepted: 9 August 2001 / Published online: 20 December 2001 相似文献
7.
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
8.
Laser driven shocks can lead to a dynamic failure, called film spallation. Here, we use a modified laser spallation set-up
to measure the dynamic adhesion of thin films and we propose a novel diagnostic technology. Based on correlation theory, new
spallation criteria for characterizing the progressive damage at the interface between the film and the substrate are established,
such as interface delamination, film spallation and film expulsion. With the help of the theory, the degree of damage and
the dimension of damage (i.e. fracture), such as the minimum width of delamination radius, the thickness of the film etc.,
are estimated. Experiments are carried out on epoxy/stainless steel and epoxy/Al, and the experimental results show that their
dynamic bonding strengths are about 25 MPa and 20 MPa, respectively. The detailed results, analyses and discussions are presented
in this paper.
Received: 6 February 2001 / Accepted: 3 December 2001 / Published online: 11 February 2002 相似文献
9.
Laser-induced periodic surface structures (LIPSS) were generated on oriented and amorphous thick, as well as on spin-coated
thin, poly-carbonate films by polarized ArF excimer laser light. The influence of the film structure and thickness on the
LIPSS formation was demonstrated. Below a critical thickness of the spin-coated films the line-shaped structures transformed
into droplets. This droplet formation was explained by the laser-induced melting across the whole film thickness and subsequent
de-wetting on the substrate. The thickness of the layer melted by laser illumination was computed by a heat-conduction model.
Very good agreement with the critical thickness for spin-coated films was found. The original polymer film structure influences
the index of refraction of the thin upper layer modified by the laser treatment, as was proven by the dependence of the structure’s
period on the angle of incidence both for ‘s’- and ‘p’-polarized beams. The effect of the original surface roughness – grains in thick films or holes in thin films –
was studied using atomic force microscopy. It was shown that the oblique incidence of ‘s’-polarized beams results in an intensity confinement in the direction of the forward scattering and in asymmetrical interference
pattern formation around these irregularities. A new, two-dimensional grating-like structure was generated on spin-coated
films. These gratings might be used as a special kind of mask.
Received: 10 July 2001 / Accepted: 23 July 2001 / Published online: 30 August 2001 相似文献
10.
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
11.
Youwei Tian Xun Wang Huanhuan Liu Hongtao Huang Xue Qin Vinod Senecha 《Optical and Quantum Electronics》2012,44(8-9):393-401
The comparative efficiency and beam characteristics of high-energy ions generated from the interaction of a petawatt laser pulse with thin foil target and a small solid-density plasma bunch target have been studied by particle-in-cell simulation under identical conditions. It is shown that thin foil and small solid dense target of micrometer size can be efficiently accelerated when irradiated by a laser pulse of intensity >1021?W/cm2. Using direct beam measurements, we find that small solid dense target acceleration produces higher energy particles with smaller divergence and a higher efficiency compared to thin foil target acceleration. The merits of small solid target acceleration can be exploited for potential applications such as its role as ignitor for fast ignition in inertial confinement fusion. 相似文献
12.
S. Bollanti F. Bonfigli E. Burattini P. Di Lazzaro F. Flora A. Grilli T. Letardi N. Lisi A. Marinai L. Mezi D. Murra C. Zheng 《Applied physics. B, Lasers and optics》2003,76(3):277-284
A long-pulse-width high-output energy (120 ns FWHM, 7 J) XeCl laser has been focused on thin tape targets (Cu and Ta) to generate
more than 100-ns-long (FWHM) EUV pulses in the 10–30 nm spectral region, suitable for projection microlithography. The conversion
efficiency was more than 20% over a 2π solid angle. We observed debris emission using a gated CCD camera, and measured the
debris speed for different irradiation conditions. We found irradiation conditions such that the measured velocities were
low enough that simple mechanical devices combined with krypton at low-pressure could efficiently stop both ionic debris and
cluster debris. Our results show that a suitable combination of driving-laser characteristics, target material and thickness,
environment gas and mechanical choppers can make clean and increase the power of EUV solid-target laser-plasma sources.
Received: 21 October 2002 / Published online: 26 February 2003
RID="*"
ID="*"Corresponding author. Fax: +39-06/9400-5334, E-mail: bollanti@frascati.enea.it 相似文献
13.
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
14.
Femtosecond ablation of ultrahard materials 总被引:4,自引:0,他引:4
G. Dumitru V. Romano H.P. Weber M. Sentis W. Marine 《Applied Physics A: Materials Science & Processing》2002,74(6):729-739
Several ultrahard materials and coatings of definite interest for tribological applications were tested with respect to their
response when irradiated with fs laser pulses. Results on cemented tungsten carbide and on titanium carbonitride are reported
for the first time and compared with outcomes of investigations on diamond and titanium nitride. The experiments were carried
out in air, in a regime of 5–8 J/cm2 fluences, using the beam of a commercial Ti:sapphire laser. The changes induced in the surface morphology were analysed with
a Nomarski optical microscope, and with SEM and AFM techniques. From the experimental data and from the calculated incident
energy density distributions, the damage and ablation threshold values were determined. As expected, the diamond showed the
highest threshold, while the cemented tungsten carbide exhibited typical values for metallic surfaces. The ablation rates
determined (under the above-mentioned experimental conditions) were in the range 0.1–0.2 μm per pulse for all the materials
investigated.
Received: 31 August 2001 / Accepted: 3 December 2001 / Published online: 20 March 2002 相似文献
15.
S. Düsterer H. Schwoerer W. Ziegler C. Ziener R. Sauerbrey 《Applied physics. B, Lasers and optics》2001,73(7):693-698
We optimize the conversion of laser energy into extreme ultraviolet (EUV) radiation by tailoring the laser parameters for
a laser-produced plasma generated from 20 μm diameter water droplets. It is shown that mass-limited targets require careful
adaption of laser-pulse energy and laser-pulse duration separately, rather than laser intensity, which seems to be adequate
for bulk targets. The optimal pulse duration scales with the droplet radius, and the optimal pulse energy with the droplet
volume. With optimized parameters, we obtain a conversion efficiency of 0.23% in 4π and 2.5% bandwidth for 13 nm radiation,
the future EUV lithography light.
Received: 16 July 2001 / Revised version: 25 September 2001 / Published online: 7 November 2001 相似文献
16.
A systematic theoretical study of laser-irradiated targets made of material with increasing atomic number has been performed.
The formation of energetic light ions resulting from the interaction of an intense ultrashort pulse laser with thin planar
targets is investigated theoretically with a two-dimensional relativistic electromagnetic particle-in-cell model. A common
parameter, the areal electron density of the foil, can be used to describe qualitatively targets made of different material.
By varying either the laser intensity or the target thickness we observe a gradual transition of various ion acceleration
mechanisms from one into another. Light ions, such as H+, Li3+, C6+, and Al13+, can be accelerated to GeV energies with existing laser systems at a laser fluence of 10–20 J/μm2. 相似文献
17.
M. Vogel K. Hansen A. Herlert L. Schweikhard 《Applied physics. B, Lasers and optics》2001,73(4):411-416
The pathway competition between neutral monomer and neutral dimer evaporation from optically excited odd-size gold cluster
ions Au+
n, n=7–15, has been investigated as a function of cluster size and excitation energy. Gold cluster ions of these sizes are
the only ones to show observable pathway competition while all other sizes exclusively evaporate either neutral monomers or
neutral dimers. The investigation has been performed by photoexcitation of stored size-selected gold cluster ions with a single
10-ns laser pulse. Subsequent time-resolved observation of the delayed dissociation allows us to quantitatively determine
the relative fragment yields of the respective decay channels as a function of excitation energy. Contrary to theoretical
expectations, the dimer-to-monomer branching ratio of evaporated particles is found to decrease monotonously with increasing
excitation energy for all cluster sizes under investigation. Possible explanations for this behaviour are discussed.
Received: 9 July 2001 / Revised version: 24 September 2001 / Published online: 15 October 2001 相似文献
18.
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
19.
Y. Sentoku V.Y. Bychenkov K. Flippo A. Maksimchuk K. Mima G. Mourou Z.M. Sheng D. Umstadter 《Applied physics. B, Lasers and optics》2002,74(3):207-215
Multi-MeV ion production from the interaction of a short laser pulse with a high-density plasma, accompanied by an underdense
preplasma, has been studied with a particle-in-cell simulation and good agreement is found with experiment. The mechanism
primarily responsible for the acceleration of ions is identified. Comparison with experiments sheds light on the ion-energy
dependence on laser intensity, preplasma scale length, and relative ion energies for a multi-species plasma. Two regimes of
maximum ion-energy dependence on laser intensity, I, have been identified: subrelativistic, ∝I; and relativistic, ∝. Simulations show that the energy of the accelerated ions versus the preplasma scale length increases linearly and then saturates.
In contrast, the ion energy decreases with the thickness of the solid-density plasma.
Received: 13 December 2001 / Published online: 7 February 2002 相似文献
20.
C.D. Scott S. Arepalli P. Nikolaev R.E. Smalley 《Applied Physics A: Materials Science & Processing》2001,72(5):573-580
Mechanisms proposed in the literature are compared with a current scenario for the formation of single-wall carbon nanotubes
in the laser-ablation process that is based on our spectral emission and laser-induced fluorescence measurements. It is suggested
that the carbon which serves as feedstock for nanotube formation not only comes from the direct ablation of the target, but
also from carbon particles suspended in the reaction zone. Fullerenes formed in the reaction zone may be photo-dissociated
into C2 and other low molecular weight species, and also may serve as feedstock for nanotube growth. Confinement of the nanotubes
in the reaction zone within the laser beam allows the nanotubes to be ‘purified’ and annealed during the formation process
by laser heating.
Received: 2 November 2000 / Accepted: 3 November 2000 / Published online: 23 March 2001 相似文献