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1.
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
2.
The micromachining of hydroxyapatite (HAp) is highly important for orthopedics and dentistry, since human bone and teeth consist
mainly of HAp. We demonstrate ultrashort Ti:sapphire laser ablation of HAp, using pulse-widths of 50 fs, 500 fs, and 2 ps
at a wavelength of 820 nm and at 1 kpps. The crucial medical issue is to preserve the chemical properties of the machined
(ablated) surface. If the chemical properties of HAp change, the human bone or tooth cannot re-grow after laser processing.
Using X-ray photoelectron spectroscopy, we observe chemical properties of HAp ablated in air. The HAp is ablated at laser
fluences of 3.2 J/cm2 (6.4×1013 W/cm2 at 50 fs), 3.3 J/cm2 (6.6×1012 W/cm2 at 500 fs), and 9.6 J/cm2 (4.8×1012 W/cm2 at 2 ps), respectively. As a result it is found that the ablated surface is unchanged after laser ablation over the pulse-width
range used in this experiment.
Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-45/566-1533, E-mail: obara@obara.elec.keio.ac.jp 相似文献
3.
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
4.
Tungsten microcone arrays with a high aspect ratio are formed by the cumulative nanosecond pulsed-Nd:YAG laser irradiation
of single-crystal tungsten under low pressure in an inert atmosphere. The morphology of the microcones and their density were
strongly affected by the number of laser pulses. The microcones grew to a length of 20 μm with a diameter of about 1.5 μm
at the tip after irradiation with more than 1200 pulses under our experimental conditions. They may have potential applications
for emission cathodes in a field-emission display (FED) and in microelectronic devices.
Received: 8 January 2001 / Accepted: 13 June 2001 / Published online: 2 October 2001 相似文献
5.
Bulk heating of transparent materials using a high-repetition-rate femtosecond laser 总被引:7,自引:0,他引:7
C.B. Schaffer J.F. García E. Mazur 《Applied Physics A: Materials Science & Processing》2003,76(3):351-354
Femtosecond laser pulses can locally induce structural and chemical changes in the bulk of transparent materials, opening
the door to the three-dimensional fabrication of optical devices. We review the laser and focusing parameters that have been
applied to induce these changes and discuss the different physical mechanisms that play a role in forming them. We then describe
a new technique for inducing refractive-index changes in bulk material using a high-repetition-rate femtosecond oscillator.
The changes are caused by a localized melting of the material, which results from an accumulation of thermal energy due to
nonlinear absorption of the high-repetition-rate train of laser pulses.
Received: 21 November 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +1-858/534-7697, E-mail: cschaffer@ucsd.edu
RID="**"
ID="**"Current address: University of California, San Diego, Department of Physics, La Jolla, CA 92 093, USA 相似文献
6.
A.A. Babin D.V. Kartashov A.M. Kiselev V.V. Lozhkarev A.N. Stepanov A.M. Sergeev 《Applied physics. B, Lasers and optics》2002,75(4-5):509-514
. We report on the experimental and theoretical study of spectrum transformation and frequency blue-shift of femtosecond laser
pulses with intensities up to 2×1016 W/cm2, propagating in glass capillary tubes under gas ionization. Monomode optical guiding with 45% transmission efficiency is
demonstrated in a 100-μm-diameter, 20-cm length capillary. A broadening of the initial spectrum as much as several initial
spectrum widths is achieved. Besides the broadening, the mean frequency of the output radiation in the spectrum experiences
a blue-shift of up to several initial spectrum widths, caused by the non-stationary, non-linear process of gas ionization.
Our numerical simulations, in the form of a simple one-dimensional model for the propagation of intense laser pulses in gas-filled
capillaries, are in good qualitative agreement with the experimental results. These simulations show the possibility of significant
compression of an output pulse in a simple compression scheme (e.g. a piece of silica glass with normal dispersion), which
is very important for obtaining laser pulses with few optical cycles at the millijoule energy level.
Received: 25 September 2001 / Revised version: 6 December 2001 / Published online: 25 September 2002
RID="*"
ID="*"Corresponding author. Fax: +7-8312/363-792, E-mail: dekart@ufp.appl.sci-nnov.ru 相似文献
7.
Absolute frequency measurement of iodine lines with a femtosecond optical synthesizer 总被引:2,自引:0,他引:2
R. Holzwarth A.Yu. Nevsky M. Zimmermann Th. Udem T.W. Hänsch J. von Zanthier H. Walther J.C. Knight W.J. Wadsworth P.St.J. Russell M.N. Skvortsov S.N. Bagayev 《Applied physics. B, Lasers and optics》2001,73(3):269-271
We have used a single laser femtosecond optical frequency synthesizer together with a widely tunable Nd:YAG laser to measure
the absolute frequency of several absorption lines in molecular iodine around 532 nm. The use of two different repetition
frequencies allows us to determine the number of modes used for the frequency measurement unambiguously. The lines also provide
data for the determination of improved ro-vibrational constants of the iodine molecule.
Received: 3 July 2001 / Published online: 19 September 2001 相似文献
8.
Modification of the fused silica glass network associated with waveguide fabrication using femtosecond laser pulses 总被引:1,自引:0,他引:1
J.W. Chan T.R. Huser S.H. Risbud D.M. Krol 《Applied Physics A: Materials Science & Processing》2003,76(3):367-372
Atomic-scale structural changes have been observed in the glass network of fused silica after modification by tightly focused
800-nm, 130-fs laser pulses at fluences between 5 and 200 J cm-2. Raman spectroscopy of the modified glass shows an increase in the 490 and 605-cm-1 peaks, indicating an increase in the number of 4- and 3-membered ring structures in the silica network. These results provide
evidence that densification of the glass occurs after exposure to fs pulses. Fluorescence spectroscopy of the modified glass
shows a broad fluorescence band at 630 nm, indicating the formation of non-bridging oxygen hole centers (NBOHC) by fs pulses.
Waveguides that support the fundamental mode at 633 nm have been fabricated inside fused silica by scanning the glass along
the fs laser beam axis. The index changes are estimated to be approximately 0.07×10-3.
Received: 17 December 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +1-925/423-2463, E-mail: dmkrol@ucdavis.edu 相似文献
9.
Remote sensing of the atmosphere using ultrashort laser pulses 总被引:2,自引:0,他引:2
P. Rairoux H. Schillinger S. Niedermeier M. Rodriguez F. Ronneberger R. Sauerbrey B. Stein D. Waite C. Wedekind H. Wille L. Wöste C. Ziener 《Applied physics. B, Lasers and optics》2000,71(4):573-580
Theoretical and experimental studies were performed on the propagation of ultrashort optical terawatt pulses through the atmosphere.
Propagation simulations of intense sub-picosecond pulses show that non-linear processes, such as white light generation, can
be initiated at a chosen distance by selecting an appropriate group velocity dispersion. With this technique, a white light
continuum was generated in the atmosphere whose spectral distribution was characterised in the visible and near infra-red.
Applications of this novel light source for atmospheric remote sensing were investigated, combining lidar and time-resolved
broadband absorption spectroscopy techniques. Measurements were performed on the oxygen molecule and water vapour. A comparison
between the experimental results and the tabulated spectroscopic data led to an excellent correlation with measurements made
on water vapour whereas observations on the oxygen showed discrepancy. This study demonstrates that the remote generation
of a white light source represents a new way to access the range-resolved multi-trace gas analysis in the atmosphere.
Received: 8 December 1999 / Revised version: 18 May 2000 / Published online: 16 August 2000 相似文献
10.
M. Lorenc M. Ziolek R. Naskrecki J. Karolczak J. Kubicki A. Maciejewski 《Applied physics. B, Lasers and optics》2002,74(1):19-27
The paper discusses three different artifacts related to two-photon absorption (TPA), stimulated Raman amplification (SRA)
and cross-phase modulation (XPM), all intrinsic to transient absorption measurements with femtosecond time resolution. Certain
properties of these signals are analysed and shown to superimpose onto measured transient absorption spectra. Ways of reducing
the influence of the artifacts discussed are suggested. A simple correcting procedure based on the linear intensity dependence
of the artifacts discussed is proposed.
Received: 29 May 2001 / Final version: 15 October 2001 / Published online: 29 November 2001 相似文献
11.
Laser cleaning of polymer surfaces 总被引:2,自引:0,他引:2
T. Fourrier G. Schrems T. Mühlberger J. Heitz N. Arnold D. Bäuerle M. Mosbacher J. Boneberg P. Leiderer 《Applied Physics A: Materials Science & Processing》2001,72(1):1-6
We have investigated the removal of small spherical particles from polymer surfaces by means of 193-nm ArF and 248-nm KrF
laser light. Polystyrene (PS) particles with diameters in the range of 110 nm to 1700 nm and silica particles (SiO2) with sizes of 400 nm and 800 nm are successfully removed from two different substrates, polyimide (PI) and polymethylmethacrylate
(PMMA). Experiments were performed in air (23 °C, relative humidity 24–28%) and in an environment with a relative humidity
(RH) of about 90%.
Received: 13 July 2000 / Accepted: 14 July 2000 / Published online: 9 November 2000 相似文献
12.
A method of determination of the true temporal response function for pump-probe type of experiments with femtosecond time
resolution is presented. An analytical formula allowing calculation of group velocity dispersion (GVD) modified and sample
thickness-sensitive pump-probe cross correlation function is provided. The reliability of the formula is further experimentally
verified with measurements of ultrafast stimulated Raman scattering and transient absorption signals.
Received: 31 October 2000 / Revised version: 6 February 2001 / Published online: 27 April 2001 相似文献
13.
J. Thogersen A. Borowiec H.K. Haugen F.E. McNeill I.M. Stronach 《Applied Physics A: Materials Science & Processing》2001,73(3):361-363
We characterize the spectral properties of X-rays generated from selected metal and semiconductor targets when 120-fs laser
pulses are focused to intensities of∼1014–3×1015 W/cm2 during laser micromachining in air. High fluxes of multi-keV-energy X-rays could be obtained with 280-μJ pulses at a 1 kHz
repetition rate. The yield and spectral composition of the X-rays are found to depend sensitively on the processing conditions,
and thus the X-ray emission is expected to be a novel indicator of optimal laser machining.
Received: 17 July 2000 / Accepted: 27 October 2000 / Published online: 28 February 2001 相似文献
14.
A commercial femtosecond pulse laser was used to study the interaction of ultrashort laser pulses with aluminum. Tests were conducted to measure the average drilling rate over a range of laser pulse energies in both air and vacuum at the wavelengths corresponding to the fundamental and second harmonic of the laser. For the fundamental wavelength, it was observed that the drilling rates in vacuum were significantly higher than that for drilling in atmospheric air. For the laser beam that was converted to second harmonic, the drilling rate in vacuum at the same energy was slightly lower than that for drilling in air. The observed results can be explained by the presence of an energetic nanosecond pedestal in the laser pulse produced by the femtosecond laser system. This nanosecond component provides a major contribution into drilling and it is strongly affected by the optical breakdown plasma that reduces the drilling rate in air. Conversion to second harmonic reduces the relative energy content of the nanosecond component resulting in a higher contrast femtosecond pulse that is not affected by the near surface plasma. The presence of air results in self-focusing of the second harmonic laser beam, causing an increased drilling rate as compared to the interaction in vacuum. 相似文献
15.
M. Hentschel S. Uemura Z. Cheng S. Sartania G. Tempea C. Spielmann F. Krausz 《Applied physics. B, Lasers and optics》1999,68(1):145-148
Received: 9 June 1998/Revised version: 4 November 1998 相似文献
16.
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
17.
Received: 17 December 1998 相似文献
18.
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
19.
J.M. Lee K.G. Watkins W.M. Steen 《Applied Physics A: Materials Science & Processing》2000,71(6):671-674
Laser removal of small particles from a metal surface is carried out by changing the incident angle of the laser beam. It
has been found that a dramatic improvement of cleaning efficiency in terms of area and energy is observed when using the laser
at glancing angle of incidence as compared to perpendicular. Furthermore substrate damage is greatly reduced and probably
eliminated at glancing angles. The process mechanism is discussed by considering the adhesion and the laser-induced cleaning
forces for different incident angles. It is shown that there are different laser–matter interactions operating.
Received: 25 April 2000 / Accepted: 9 May 2000 / Published online: 5 October 2000 相似文献
20.
A new method for improving the efficiency of laser drilling has been developed. Two synchronized free-running laser pulses
from a tandem-head Nd:YAG laser are capable of drilling through 1/8-in-thick stainless-steel targets at a stand-off distance
of 1 m without gas-assist. The combination of a high-energy laser pulse for melting with a properly tailored high-intensity
laser pulse for liquid expulsion results in the efficient drilling of metal targets. We argue that the improvement in drilling
is due to the recoil pressure generated by rapid evaporation of the molten material by the second laser pulse.
Received: 29 August 2000 / Accepted: 18 December 2000 / Published online: 3 April 2001 相似文献