共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Stanislawki J. Meister T. Mitra M.M. Ivanenko K. Zanger P. Hering 《Applied physics. B, Lasers and optics》2001,72(1):115-120
The Er:YAG and the CO2 laser are competitors in the field of hard tissue ablation. The use of Er:YAG lasers (2.94 μm, pulse length
L of 100 to 200 μs) show smaller areas of thermal defects then ‘‘superpulsed’’ CO2 lasers with pulse lengths of approximately 100 μs. Only the development of a Q-switched CO2 laser (9.6 μm, τL=250 ns) allowed for similar results. In this paper new results for the Er:YAG and the Q-switched CO2 laser under the influence of water spray will be presented. Several parameters are of special interest for these investigations:
the specific ablation energy, which shows a minimum for the CO2 laser at an energy density of 9 J/cm 2 and a broad shallow minimum in the range of 10 to 70 J/cm2 for the Er:YAG laser, and comparison of the cut-shape and depth. Surface effects and cutting velocity are discussed based
on SEM pictures.
Received: 19 July 2000 / Revised version: 1 November 2000 / Published online: 30 November 2000 相似文献
2.
J.M. Auerhammer R. Walker A.F.G. van der Meer B. Jean 《Applied physics. B, Lasers and optics》1999,68(1):111-119
2 . Dynamic parameters such as the extension of the ablation cloud, the initial velocity and momentum of the ablated particles
as well as the ablation threshold, the ablated mass, and the particle size were investigated. The ablation plume was made
visible with a stroboscopic technique. For a fluence of 3.1 J/cm2 the average initial velocity of the ejected particles was deduced from the extension of the plume to range from 120–400 m/s.
Measurements of the recoil momentum using a sensitive pendulum led to values between 0.5 and 2.0 mm g/s. All measured properties
were related to the spectroscopically determined absorption coefficient of cornea αcornea. Where absorption due to proteins is high (at λ=6.2 and 6.5 μm), ablated mass, velocity and recoil momentum behave according
to αcornea. For the first time, variations of the ablation plume from pulse to pulse were observed. Those, as well as the particle size,
not only depend on the absorption coefficient, but also on the predominant absorber.
Received: 4 November 1997/Revised version: 7 September 1998 相似文献
3.
Light can transform the secondary structure of silk protein 总被引:3,自引:0,他引:3
Y. Tsuboi T. Ikejiri S. Shiga K. Yamada A. Itaya 《Applied Physics A: Materials Science & Processing》2001,73(5):637-640
Fibroin is the main component of silk and is expected to be used as a novel functional material in medicine and bioelectronics.
The main secondary structures of this protein are of the random-coil and the β-sheet types. In this study, we carried out
laser-induced transformation of the secondary structure, from the random-coil type to the β-sheettype, in solid fibroin films.
We prepared two types of fibroin films with the random-coil structure. One is a fibroin film doped with a dye as a photosensitizer
with a small amount (1 wt %), and the other is a neat fibroin film. The former was excited at 532 nm and the latter was excited
at 266 nm. Irradiations were carried out with fluences much lower than each ablation threshold. The excitation of the dye
at 532 nm did not affect the secondary structure of the random-coil type. By contrast, 266-nm laser irradiation, which excites
tryptophan (an amino-acid residue) involved in fibroin, created the β-sheetdomain in the film. The structural transformation
was revealed by infrared absorption spectroscopy and atomic force microscopy.
Received: 1 August 2001 / Accepted: 2 August 2001 / Published online: 2 October 2001 相似文献
4.
J. Bonse S. Baudach J. Krüger W. Kautek M. Lenzner 《Applied Physics A: Materials Science & Processing》2002,74(1):19-25
We investigated the initial modification and ablation of crystalline silicon with single and multiple Ti:sapphire laser pulses
of 5 to 400 fs duration. In accordance with earlier established models, we found the phenomena amorphization, melting, re-crystallization,
nucleated vaporization, and ablation to occur with increasing laser fluence down to the shortest pulse durations. We noticed
new morphological features (bubbles) as well as familiar ones (ripples, columns). A nearly constant ablation threshold fluence
on the order of 0.2 J/cm2 for all pulse durations and multiple-pulse irradiation was observed. For a duration of ≈100 fs, significant incubation can
be observed, whereas for 5 fs pulses, the ablation threshold does not depend on the pulse number within the experimental error.
For micromachining of silicon, a pulse duration of less than 500 fs is not advantageous.
Received: 4 December 2000 / Revised version: 29 March 2001 / Published online: 20 June 2001 相似文献
5.
Ultrashort-pulse laser ablation of indium phosphide in air 总被引:4,自引:0,他引:4
J. Bonse J.M. Wrobel J. Krüger W. Kautek 《Applied Physics A: Materials Science & Processing》2001,72(1):89-94
Ablation of indium phosphide wafers in air was performed with low repetition rate ultrashort laser pulses (130 fs, 10 Hz)
of 800 nm wavelength. The relationships between the dimensions of the craters and the ablation parameters were analyzed. The
ablation threshold fluence depends on the number of pulses applied to the same spot. The single-pulse ablation threshold value
was estimated to be φth(1)=0.16 J/cm2. The dependence of the threshold fluence on the number of laser pulses indicates an incubation effect. Morphological and
chemical changes of the ablated regions were characterized by means of scanning electron microscopy and Auger electron spectroscopy.
Received: 30 May 2000 / Accepted: 31 May 2000 / Published online: 23 August 2000 相似文献
6.
We present observations of sub-micron- to micron-sized particles generated by high fluence (≈2 J/cm2) 248-nm laser ablation of pressed polytetrafluorethylene (PTFE) targets in air at atmospheric pressure. The original target
material was hydrostatically compressed ≈7 μm PTFE powder, sintered at 275 °C. Collected ejecta due to laser irradiation consists
of four basic particle morphologies ranging from small particles 50–200 nm in diameter to larger particles ≈10 μm in diameter.
Many particles formed in air carry electric charge. Using charged electrodes we are able to collect charged particles to determine
relative numbers of ± charge. We observe roughly equal numbers of positively and negatively charged particles except for the
largest particles which were predominantly negative. For a range of particle sizes we are able to measure the sign and magnitude
of this charge with a Millikan-oil-drop technique and determine surface charge densities. The implications of these observations
with respect to pulsed laser deposition of PTFE thin films and coatings are discussed.
Received: 15 January 1999 / Accepted: 18 January 1999 / Published online: 7 April 1999 相似文献
7.
Loesel F.H. Fischer J.P. Götz M.H. Horvath C. Juhasz T. Noack F. Suhm N. Bille J.F. 《Applied physics. B, Lasers and optics》1998,66(1):121-128
2 ; for 100 fs pulses from the same laser the experimental threshold was at 1.5 J/cm2. Histopathological examinations and scanning electron micrographs confirm the high quality of the excisions. No sign of significant
thermal damage was observed.
Received: 29 January 1997/Revised version: 14 July 1997 相似文献
8.
A.V. Karabutov V.D. Frolov E.N. Loubnin A.V. Simakin G.A. Shafeev 《Applied Physics A: Materials Science & Processing》2003,76(3):413-416
Low-threshold field electron emission (FEE) is reported for periodic arrays of micro-tips produced by laser ablation of Si
wafers. The best samples show emission at threshold fields as low as 4–5 V/μm for n-type Si substrates and of 1–2 V/μm for
p-doped Si substrates, as measured with a flat-screen technique. Auger electron spectroscopy and X-ray electron spectroscopy
reveal island-like deviation of the SiO2 stoichiometry on the tip surfaces, with lateral dimensions of less than 100 nm. Microscopic studies using a special field-emission
STM show that the emission originates from well-conducting regions of sub-micron size. The experimental data suggest FEE from
the tip arrays by a geometric field enhancement of both the individual micro-tip and the narrow conducting channels in the
tip body.
Received: 3 May 2002 / Accepted: 1 July 2002 / Published online: 28 October 2002
RID="*"
ID="*"Corresponding author. Fax: +7-095/135-82-34, E-mail: shafeev@kapella.gpi.ru 相似文献
9.
Modeling of UV pulsed-laser ablation of metallic targets 总被引:1,自引:0,他引:1
S. Amoruso 《Applied Physics A: Materials Science & Processing》1999,69(3):323-332
A model to describe the laser ablation of metallic targets is presented. It accounts for the main physical processes involved
in the laser–solid–plasma interaction by considering the photon absorption and the ionization mechanisms that are active in
the plasma, as well as the laser-produced plasma kinetics. The model is used to simulate the laser ablation of aluminum targets
irradiated with a 6-ns UV laser pulse at 0.35 μm, and the results are compared with experimental findings. Calculations show
that all the investigated plasma parameters strongly depend on the laser intensity until a roll-off is reached at irradiance
≥1.5 GW cm-2. The satisfactorily good agreement between model predictions and experimental findings confirms that laser–plasma interaction
processes and plasma kinetics play a relevant role during nanosecond laser ablation of metals in the laser intensity range
of concern in this study.
Received: 12 February 1999 / Accepted: 12 April 1999 / Published online: 7 July 1999 相似文献
10.
R.F.W. Herrmann J. Gerlach E.E.B. Campbell 《Applied Physics A: Materials Science & Processing》1998,66(1):35-42
Received: 30 July 1997/Accepted: 5 August 1997 相似文献
11.
Polarization effects in ultrashort-pulse laser drilling 总被引:1,自引:0,他引:1
S. Nolte C. Momma G. Kamlage A. Ostendorf C. Fallnich F. von Alvensleben H. Welling 《Applied Physics A: Materials Science & Processing》1999,68(5):563-567
A strong influence of the polarization of the laser radiation on the geometry of laser-machined microdrillings has been observed
for ultrashort pulses. For drillings with a certain aspect ratio, reflections at the hole walls take place, leading to a non-uniform
intensity distribution deep inside the formed hole. Experimental and theoretical results on this subject are discussed. It
is shown that a rotation of the polarization during the drilling process (“polarization trepanning”) significantly improves
the quality of the produced holes.
Received: 21 August 1998 / Accepted: 25 November 1998 / Published online: 17 March 1999 相似文献
12.
Chemical, morphological and accumulation phenomena in ultrashort-pulse laser ablation of TiN in air 总被引:1,自引:0,他引:1
J. Bonse H. Sturm D. Schmidt W. Kautek 《Applied Physics A: Materials Science & Processing》2000,71(6):657-665
Ultrashort-pulse laser ablation (τ=130 fs, λ=800 nm, repetition rate 2–20 Hz) of titanium nitride was investigated for laser
fluences between 0.3 and 4.5 J/cm2 using the direct focusing technique in air. The influence of the laser pulse number and the peak fluence was investigated
by means of several surface analytical techniques (optical microscopy, dynamic friction atomic force microscopy, scanning
Auger electron microscopy and small-spot electron spectroscopy for chemical analysis). The correlation of the results about
optical, physical and chemical properties of the irradiated areas allows us to propose a simple oxidation model, which explains
different observed phenomena associated with surface damage such as mound formation and crater widening and clarifies the
incubation behavior reported earlier for this material.
Received: 8 May 2000 / Accepted: 9 May 2000 / Published online: 13 September 2000 相似文献
13.
14.
Excimer laser polymer ablation: twenty years on 总被引:7,自引:0,他引:7
P.E. Dyer 《Applied Physics A: Materials Science & Processing》2003,77(2):167-173
Research and development in excimer laser polymer ablation has been actively pursued for some twenty years, driven by interest
in the basic science as well as by numerous applications that have emerged for this high-resolution technique for material
removal. This paper reviews some of the basic mechanistic aspects of the UV laser–polymer interaction as a prelude to dealing
with practical matters related to polymer processing by ablation. Applications in micro-machining and potential areas for
future research are briefly covered.
Received: 7 October 2002 / Accepted: 8 February 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +44-1482/465-606, E-mail: p.e.dyer@hull.ac.uk 相似文献
15.
Holographic interferometry for the structural diagnostics of UV laser ablation of polymer substrates
A. Bonarou L. Antonucci V. Tornari S. Georgiou C. Fotakis 《Applied Physics A: Materials Science & Processing》2001,73(5):647-651
Holographic interferometry is examined for its potential as a diagnostic tool of the structural modifications effected in
laser-processing applications. The interferometric ‘comparison’ of the holographic images of the sample recorded before and
after irradiation enables the full-field spatially resolved detection of the induced structural modifications. The potential
of the method is illustrated in the ablation of polymer (polymethylmethacrylate and polystyrene) films with nanosecond pulses
at 193 and 248 nm. The detailed characterization and quantitative monitoring of the growth of the induced modifications as
a function of laser-material parameters is attained. A most novel result is the observation of delocalised structural modifications
at distances relatively far away (d≈2 cm) from the irradiated area.
Received: 15 August 2001 / Accepted: 16 August 2001 / Published online: 2 October 2001 相似文献
16.
I. Okuda J. Ma E. Takahashi I. Matsushima Y. Matsumoto S. Kato Y. Owadano 《Applied physics. B, Lasers and optics》2001,72(5):623-626
The initial test results of the high-repetition-rate (rep-rate) electron-beam (e-beam) pumped KrF laser amplifier under development
in our laboratory are reported. This amplifier is aimed at producing a laser energy of 20 J per pulse at a rep rate of 1 Hz.
Thus far, 700 consecutive e-beampulses (250 kV, 270 J/pulse) were generated at a rep rate of 1 Hz. The laser gas was repetitively
pumped by the e-beams injected through the water-cooled diaphragm foils.
Received: 5 February 2001 / Published online: 21 March 2001 相似文献
17.
M. Feuerhake J.-H. Klein-Wiele G. Marowsky P. Simon 《Applied Physics A: Materials Science & Processing》1998,67(5):603-606
Received: 27 July 1998/Accepted: 28 July 1998 相似文献
18.
A. A. Serafetinides M. Makropoulou E. Fabrikesi E. Spyratou C. Bacharis R. R. Thomson A. K. Kar 《Applied Physics A: Materials Science & Processing》2008,93(1):111-116
The use of intraocular lenses (IOLs) is the most promising method to restore vision after cataract surgery. Several new materials,
techniques, and patterns have been studied for forming and etching IOLs to improve their optical properties and reduce diffractive
aberrations. This study is aimed at investigating the use of ultrashort laser pulses to ablate the surface of PMMA and intraocular
lenses, and thus provide an alternative to conventional techniques. Ablation experiments were conducted using various polymer
substrates (PMMA samples, hydrophobic acrylic IOL, yellow azo dye doped IOL, and hydrophilic acrylic IOL consist of 25% H2O). The irradiation was performed using 100 fs pulses of 800 nm radiation from a regeneratively amplified Ti:sapphire laser
system. We investigated the ablation efficiency and the phenomenology of the ablated patterns by probing the ablation depth
using a profilometer. The surface modification was examined using a high resolution optical microscope (IOLs) or atomic force
microscope—AFM (PMMA samples). It was found that different polymers exhibited different ablation characteristics, a result
that we attribute to the differing optical properties of the materials. In particular, it was observed that the topography
of the ablation tracks created on the hydrophilic intraocular lenses was smoother in comparison to those created on the PMMA
and hydrophobic lens. The yellow doped hydrophobic intraocular lenses show higher ablation efficiency than undoped hydrophobic
acrylic lenses. 相似文献
19.
Characteristics of thermo-mechanical laser ablation process are investigated using an original numerical model. In contrast
with previous models, it is based on a microscopic physical model of the micro-explosion process, which combines thermodynamic
behavior of tissue water with elastic response of the solid tissue components. Diffusion of dissipated heat is treated in
one dimension, and the amount of thermal damage is assessed using the Arrhenius model of the protein denaturation kinetics.
Influence of the pulse fluence and duration on temperature profile development, ablation threshold, and depth of thermal damage
is analyzed for the case of Er:YAG laser irradiation of human skin. Influence of mechanical properties on the ablation threshold
of soft tissue is predicted theoretically for the first time. In addition, feasibility of deep tissue coagulation with a repetitively
pulsed Er:YAG laser is indicated from the model.
Received: 9 July 1998 / Revised version: 26 February 1999 / Published online: 26 May 1999 相似文献
20.
T. Rothacher W. Lüthy H.P. Weber 《Applied Physics A: Materials Science & Processing》2001,73(2):133-136
According to UN estimations there are between 80 and 115 million activated landmines worldwide. These mines, or other unexploded
ordnance (UXO), can be triggered accidentally and kill or injure more than 2000 civilians per month. The most common explosive
in these mines is trinitrotoluene (TNT). In this paper, the potential of some of the most promising lasers for mine neutralisation
is investigated, namely an ArF laser, a KrF excimer laser and a Nd:YAG solid-state laser. We have studied the interaction
between laser beams emitting at λ=193 nm, 248 nm and 1060 nm and a bare solid sample of TNT of approximately 15 mg. Using
pulsed excimer radiation at λ=193 nm, with an energy density up to 1 J/mm2, ablation of the TNT without any deflagration has been achieved. At λ=248 nm, using the KrF excimer laser with a pulse duration
of 30 ns and a repetition rate of 5 Hz, the TNT sample started melting and burning after an irradiation of 10 s. Preliminary
results with the Nd:YAG solid-state laser operating in cw emission have shown that the irradiated sample exhibits the desired
burning behaviour even after the exposure is stopped.
Received: 14 December 2000 / Accepted: 18 December 2000 / Published online: 20 June 2001 相似文献