共查询到20条相似文献,搜索用时 31 毫秒
1.
C. Keyser G. Schriever M. Richardson E. Turcu 《Applied Physics A: Materials Science & Processing》2003,77(2):217-221
The water droplet laser plasma source has been shown to have many attractive features as a continuous, almost debris-free
source for extreme ultraviolet (EUV) and X-ray applications. Through a dual experimental and theoretical study, we analyze
the interaction physics between the laser light and the target. The hydrodynamic laser plasma simulation code, Medusa103 is
used to model the electron density distribution for comparison to electron density distributions obtained through Abel inversion
of plasma interferograms. In addition, flat field EUV spectra are compared to synthetic spectra calculated with the atomic
physics code RATION.
Received: 31 October 2002 / Accepted: 8 February 2003 / Published online: 28 May 2003
RID="*"
ID="*"Present address: Naval Reseach Laboratory, Washington D.C.
RID="**"
ID="**"Present address: Xtreme Technologies, G?ttingen, Germany.
RID="***"
ID="***"Corresponding author. Fax: +1-407/823-3570, E-mail: mrichard@mail.ucf.edu 相似文献
2.
Düsterer S. Schwoerer H. Ziegler W. Salzmann D. Sauerbrey R. 《Applied physics. B, Lasers and optics》2003,76(1):17-21
The influence of prepulses on the conversion efficiency (CE) of laser radiation into 13 nm extreme ultraviolet (EUV) radiation,
resulting from lithium-like oxygen ions from O20 μm water droplets, was investigated. The laser pulse durations in the experiment
ranged from 200 fs to 120 ps. Applying prepulses preceding the main pulse at various delays of up to 11 ns, it was shown that
the CE increases differently for each measured pulse duration. The strongest dependence on the introduction of a prepulse
was observed for 2 ps laser pulses with a 20 mJ laser pulse energy. The EUV CE was improved by a factor of 15 by the introduction
of a prepulse. Calculations on the atomic physics of oxygen ions and simulations of the laser–plasma interaction revealed
the influence of the prepulse on the EUV yield.
Received: 25 October 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +49-3641/947-202, E-mail: duesterer@ioq.uni-jena.de 相似文献
3.
Deep drilling of metals by femtosecond laser pulses 总被引:3,自引:0,他引:3
G. Kamlage T. Bauer A. Ostendorf B.N. Chichkov 《Applied Physics A: Materials Science & Processing》2003,77(2):307-310
Results of recent investigations on deep drilling of metals by femtosecond laser pulses are reported. At high laser fluences,
well above the ablation threshold, femtosecond lasers can drill deep, high-quality holes in metals without any post-processing
or special gas environment. It is shown that for high-quality drilling of metals, the following processes are important: (1)
laser-induced optical breakdown of air containing metal vapor and small metal particles (debris) generated by multi-pulse
femtosecond laser ablation, (2) transformation of laser pulses into light filaments, and (3) low-fluence finishing.
Received: 15 November 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-511/2788-100, E-mail: ch@lzh.de 相似文献
4.
T. Lippert M. Hauer C.R. Phipps A. Wokaun 《Applied Physics A: Materials Science & Processing》2003,77(2):259-264
The ablation characteristics of various polymers were studied at low and high fluences for an irradiation wavelength of 308 nm.
The polymers can be divided into three groups, i.e. polymers containing triazene groups, designed ester groups, and reference
polymers, such as polyimide. The polymers containing the photochemically most active group (triazene) exhibit the lowest thresholds
of ablation (as low as 25 mJ cm-2) and the highest etch rates (e.g. 250 nm/pulse at 100 mJ cm-2), followed by the designed polyesters and then polyimide. Neither the linear nor the effective absorption coefficients have
a clear influence on the ablation characteristics. The different behavior of polyimide might be explained by a pronounced
thermal part in the ablation mechanism. The laser-induced decomposition of the designed polymers was studied by nanosecond
interferometry and shadowgraphy. The etching of the triazene polymer starts and ends with the laser pulse, indicating photochemical
ablation. Shadowgraphy reveals mainly gaseous products and a pronounced shockwave in air. The designed polymers were tested
for an application as the polymer fuel in laser plasma thrusters.
Received: 21 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +41-56/3104-412, E-mail: thomas.lippert@psi.ch 相似文献
5.
T. Ohkubo M. Kuwata B. Luk’yanchuk T. Yabe 《Applied Physics A: Materials Science & Processing》2003,77(2):271-275
The CIP method is used to calculate macroscopic plume expansion combined with the Zeldovich–Raiser theory for the cluster-formation
process such as nucleation and growth. The effect of background gas and latent heat is examined in the one-dimensional case.
The latent heats keep the plume temperature at 2500 K for a long period and this explains the delayed photoluminescence. Two
contradicting experiments on the size dependence on ambient pressure are clearly explained and are attributed to the difference
of laser energy. In two-dimensional simulation, a ‘mushroom-like’ plume shape is replicated, consistent with experimental
results.
Received: 17 January 2003 / Accepted: 8 February 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-3-5237-2860, E-mail: tohkubo@es.titech.ac.jp 相似文献
6.
M. Yorozu J. Yang Y. Okada T. Yanagida F. Sakai S. Ito A. Endo 《Applied physics. B, Lasers and optics》2003,76(3):293-297
Polarization-dependent spatial beam profiles of femtosecond X-ray pulses generated by a laser Compton scheme were measured.
The X-ray pulses were generated by the interaction at an angle of 90° between 100-fs laser light and a 3-ps, 3π-mm mrad electron
beam. The polarization of the laser light was linear in two different directions, either parallel or perpendicular to the
electron beam axis. The measured profiles showed good agreement with theoretical results.
Received: 5 July 2002 / Revised version: 17 October 2002 / Published online: 5 February 2003
RID="*"
ID="*"Corresponding author. Fax: +81-424/684477, E-mail: msf_yorozu@shi.co.jp 相似文献
7.
W. Liu O. Kosareva I.S. Golubtsov A. Iwasaki A. Becker V.P. Kandidov S.L. Chin 《Applied physics. B, Lasers and optics》2003,76(3):215-229
The competition between femtosecond laser pulse induced optical breakdown and femtosecond laser pulse filamentation in condensed
matter is studied both experimentally and numerically using water as an example. The coexistence of filamentation and breakdown
is observed under tight focusing conditions. The development of the filamentation process from the creation of a single filament
to the formation of many filaments at higher pulse energy is characterized systematically. In addition, strong deflection
and modulation of the supercontinuum is observed. They manifest themselves at the beginning of the filamentation process,
near the highly disordered plasma created by optical breakdown at the geometrical focus.
Received: 9 July 2002 / Revised version: 15 November 2002 / Published online: 19 March 2003
RID="*"
ID="*"Corresponding author. Fax: +1-418/6562-623, E-mail: wliu@phy.ulaval.ca 相似文献
8.
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
9.
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
10.
Laser plasma thruster 总被引:5,自引:0,他引:5
Luke J.R. Phipps C.R. McDuff G.G. 《Applied Physics A: Materials Science & Processing》2003,77(2):343-348
The laser plasma thruster (LPT) is a new microthruster for small satellites. We report on development and testing of a prototype
LPT. Some advantages of the LPT are: thruster voltage 4 V, mass less than 1 kg, power-to-thrust ratio 10 kW/N, and Isp up to 1000 s. Typical thrust level is 250 μN with PVC fuel. Thrust of 1 mN is expected with energetic fuel. The pre-prototype
continuous-thrust experiment includes the laser mount and heat sink, lens mounts, and focusing mechanism, which are coupled
to the target-material transport mechanism. The target material is applied to a transparent plastic tape, and the laser is
focused on a series of tracks on the tape. The tape-drive hardware and laser-drive electronics are described. Design, construction,
and calibration of the thrust stand are described. During continuous operation, the exhaust plume is deflected in the direction
of the moving tape. When the laser is operated in pulsed mode, the exhaust plume is perpendicular to the tape (parallel to
the optical axis). This provides some thrust-vector control. Measured thrust is 70 μN with PVC fuel, and 550 μN with energetic
fuel, with a specific impulse of 350 s.
Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-505-272-7203, E-mail: luke@iera.nmt.edu 相似文献
11.
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
12.
Korte F. Serbin J. Koch J. Egbert A. Fallnich C. Ostendorf A. Chichkov B.N. 《Applied Physics A: Materials Science & Processing》2003,77(2):229-235
Detailed investigations of the possibilities for using femtosecond lasers for the nanostructuring of metal layers and transparent
materials are reported. The aim is to develop a simple laser-based technology for fabricating two- and three-dimensional nanostructures
with structure sizes on the order of several hundred nanometers. This is required for many applications in photonics, for
the fabrication of photonic crystals and microoptical devices, for data storage, displays, etc. Measurements of thermionic
electron emission from metal targets, which provide valuable information on the dynamics of femtosecond laser ablation, are
discussed. Sub-wavelength microstructuring of metals is performed and the minimum structure size that can be fabricated in
transparent materials is identified. Two-photon polymerization of hybrid polymers is demonstrated as a promising femtosecond
laser-based nanofabrication technology.
Received: 20 November 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-511/2788-100, E-mail: ch@lzh.de 相似文献
13.
S. Tzortzakis G. Méchain G. Patalano M. Franco B. Prade A. Mysyrowicz 《Applied physics. B, Lasers and optics》2003,76(5):609-612
We report the first observation of the attachment of two single plasma filaments created collinearly in the atmosphere by
IR femtosecond laser pulses. The linked filamentary structure is electrically conductive and emits sub-THz radiation over
its entire length. Concatenation is achieved only for a specific time ordering between the two initial laser pulses. The pulse
producing the filament closer to the laser source must be retarded with respect to the other pulse. This special time ordering
is attributed to the acceleration of light in a self-guided pulse.
Received: 4 March 2003 / Published online: 14 May 2003
RID="*"
ID="*"Corresponding author. Fax: +33-1/6931-9996, E-mail: stzortz@ensta.fr 相似文献
14.
N. Bärsch K. Körber A. Ostendorf K.H. Tönshoff 《Applied Physics A: Materials Science & Processing》2003,77(2):237-242
Although lasers are generally able to machine silicon, the major material in many microsystems applications, doing so without
influencing the physical properties of the bulk material remains an important challenge. Ultrafast lasers, in particular,
with their potential to precisely ablate all kinds of solid materials, are able to perform such processes with high efficiency
and accuracy. This article starts with an overview of the general interaction of ultrafast laser radiation with semiconductors,
explaining the absorption processes and different fluence regimes for the ablation of silicon. Major parameter influences,
especially for cutting processes in thin silicon, are described. By varying pulse energies, beam shaping methods, the beam
polarization, and temperatures, the cutting quality and speed can be significantly influenced. One important quality aspect,
besides kerf widths and surface roughness, is the amount of back-side chipping when cutting brittle materials. Achievements
in speed enhancement using linear focus shapes are presented, with cutting speeds up to five times higher than by conventional
spot-focusing. On the other hand, laser processes that cut with a spot focus offer the possibility of free-shape cutting,
which is explained using the example of wafers carrying silicon chips with highly increased package densities.
Received: 10 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-511/2788-100, E-mail: nb@lzh.de 相似文献
15.
Random deflection of the white light beam during self-focusing and filamentation of a femtosecond laser pulse in water 总被引:1,自引:0,他引:1
W. Liu O. Kosareva I.S. Golubtsov A. Iwasaki A. Becker V.P. Kandidov S.L. Chin 《Applied physics. B, Lasers and optics》2002,75(4-5):595-599
Ti:sapphire femtosecond laser pulse filamentation in competition with optical breakdown in condensed matter is studied both
experimentally and numerically using water as an example. Strong random deflection and modulation of the supercontinuum under
tight focusing conditions were observed. They manifest the beginning of the filamentation process near the highly disordered
plasma created by optical breakdown at the geometrical focus.
Received: 13 June 2002 / Revised version: 16 August 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +1-418/656-2623, E-mail: wliu@phy.ulaval.ca 相似文献
16.
M. Hauer D.J. Funk T. Lippert A. Wokaun 《Applied Physics A: Materials Science & Processing》2003,77(2):297-301
Commercially available polymers often exhibit quite poor laser ablation properties for irradiation wavelengths around 248 nm.
At these wavelengths, the absorption is due to photostable aromatic groups. Photolabile triazene polymers were developed to
compare the influence of a photolabile group on the laser ablation process. The photochemically active triazene group has
a strong absorption band at 332 nm, whereas the second absorption maximum at 220 nm is due to the photostable aromatic group.
By irradiating at 308 nm and 193 nm, the influence of the photochemically active group on the ablation process can be studied.
The etching of the triazene polymer starts and ends with the laser pulse. No surface swelling, which is assigned to photothermal
ablation, is detected for fluences above the threshold of ablation. The expansion of the laser ablation induced shockwave
was measured for the photolabile triazene polymer and the photostable polyimide. The speed of the shockwave increases with
fluence and is higher for irradiation with 193 nm than with 308 nm. A shockwave with equal or higher velocity is observed
for the triazene polymer compared with polyimide.
Received: 28 August 2002 / Accepted: 20 September 2002 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +41-56/310-4412, E-mail: thomas.lippert@psi.ch 相似文献
17.
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
18.
C.F. Wisniewski K.B. Hewett G.C. Manke II P.G. Crowell C.R. Truman G.D. Hager 《Applied Physics A: Materials Science & Processing》2003,77(2):337-342
The overtone gain medium of a small-scale HF overtone laser was probed using a sub-Doppler tunable diode laser. Two-dimensional
spatially resolved small signal gain and temperature maps were generated for several ro-vibrational transitions in the HF
(v=2→v=0) overtone band. Our results compare well with previous measurements of the overtone gain in a similar HF laser device.
Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-505/846-4807, E-mail: kevin.hewett@kirtland.af.mil 相似文献
19.
K. Sugioka K. Obata M.H. Hong D.J. Wu L.L. Wong Y.F. Lu T.C. Chong K. Midorikawa 《Applied Physics A: Materials Science & Processing》2003,77(2):251-257
Hybrid laser processing for the precision microfabrication of glass materials, in which the interaction of a conventional
pulsed laser beam and a medium on the material surface leads to effective ablation and modification, is reviewed. A major
role of the medium is to produce strong absorption of the conventional laser beam by the material. Simultaneous irradiation
by a vacuum ultraviolet (VUV) laser beam that possesses an extremely small laser fluence and an ultraviolet (UV) laser greatly
improves the ablation quality and modification efficiency for fused silica (VUV-UV multiwavelength excitation process). The
metal plasma generated by the laser beam effectively assists high-quality ablation of transparent materials by the same laser
beam, resulting in microstructuring, cutting, color marking, printing, and selective metallization of glass materials (laser-induced
plasma-assisted ablation (LIPAA)). The detailed discussion presented here includes the ablation mechanism of hybrid laser
processing.
Received: 18 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-48/462-4682, E-mail: ksugioka@postman.riken.go.jp 相似文献
20.
Measurement of filament length generated by an intense femtosecond laser pulse using electromagnetic radiation detection 总被引:4,自引:0,他引:4
We present a new method to measure the length of a filament induced by the propagation of intense femtosecond laser pulses
in air. We used an antenna to detect electromagnetic pulses radiated from multipole moments inside the filament oscillating
at the plasma frequency. The results are compared with the values detected from the backscattered fluorescence induced by
multiphoton ionization of nitrogen molecules excited inside the filament. The values are found to be in good agreement.
Received: 6 November 2002 / Revised version: 27 January 2003 / Published online: 24 April 2003
RID="*"
ID="*"Corresponding author. Fax: +1-418/656-2623, E-mail: shosseini@phy.ulaval.ca 相似文献