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1.
The selective ablation of thin (∼100 nm) SiO2 layers from silicon wafers has been investigated by applying ultra-short laser pulses at a wavelength of 800 nm with pulse
durations in the range from 50 to 2000 fs. We found a strong, monotonic decrease of the laser fluence needed for complete
ablation of the dielectric layer with decreasing pulse duration. The threshold fluence for 100% ablation probability decreased
from 750 mJ/cm2 at 2 ps to 480 mJ/cm2 at 50 fs. Significant corruption of the opened Si surface has been observed above ∼1200 mJ/cm2, independent of pulse duration. By a detailed analysis of the experimental series the values for melting and breaking thresholds
are obtained; the physical mechanisms responsible for the significant dependence on the laser pulse duration are discussed. 相似文献
2.
C. W. Cheng W. C. Shen C. Y. Lin Y. J. Lee J. S. Chen 《Applied Physics A: Materials Science & Processing》2010,101(2):243-248
A method is proposed for the fabrication of micro/nano crystalline indium tin oxide (c-ITO) structures using a Ti:Sapphire
laser with a repetition rate of 1 kHz and a wavelength of 800 nm. In the proposed approach, an amorphous ITO (a-ITO) thin
film is transformed into a c-ITO micro/nano structure over a predetermined area via laser beam irradiation, and the residual
a-ITO thin film is then removed using an etchant solution. The fabricated c-ITO structures are observed using scanning electron
microscopy (SEM) and cross-sectional transmission electron microscopy (TEM). The observation results show that the use of
a low repetition rate laser induces a high thermal cycling effect within the ITO film and therefore prompts the formation
of micro-cracks in the c-ITO structure. In addition, it is shown that as the laser power approaches the ablation threshold
of the a-ITO thin film, nanogratings and disordered nanostructures are formed along the center lines of the c-ITO patterns
formed using linearly polarized and circularly polarized laser beam irradiation, respectively. The nanogratings are found
to have a period of approximately 200 nm (i.e. one-quarter of the irradiation wavelength), while the nanostructures have an
average diameter of approximately 100–160 nm. 相似文献
3.
Irina N. Zavestovskaya Peter G. Eliseev Oleg N. Krokhin Natalia A. Men’kova 《Applied Physics A: Materials Science & Processing》2008,92(4):903-906
The mechanisms of nonlinear absorption in transparent materials under irradiation with ultrashort laser pulses are considered
theoretically. Nitride semiconductor, sapphire and others transparent dielectrics were investigated. The ablation threshold
for these materials is within multi-TW/cm2 range. The model was used based on the tunneling absorption under the irradiation by high-intensity ultrashort pulses in
terms of the theory of ionization of solid in a field of strong electromagnetic wave. The effect of the energy gap of material
on the threshold of laser ablation was adequately explained. 相似文献
4.
A. Rodenberg S. Fechner F. Dimler D. J. Tannor T. Brixner 《Applied physics. B, Lasers and optics》2008,93(4):763-772
The characterization and interpretation of ultrashort laser pulses is most intuitive in the joint time–frequency domain, where
structures like multiple pulses become immediately apparent. For practical reasons, ultrafast femtosecond laser pulse shaping,
however, is commonly carried out in the frequency domain. Here we implement pulse shaping of optical fields defined in the
von Neumann representation, which is a joint time–frequency distribution with complex-valued Gaussian basis functions. We
discuss the feasibility as well as the principal limitations of this technique, show illustrative examples, and propose possible
applications in coherent control. 相似文献
5.
C. Dölle C. Reinhardt P. Simon B. Wellegehausen 《Applied physics. B, Lasers and optics》2002,75(6-7):629-634
. Investigations of the efficient generation of powerful coherent radiation at 82.8 nm by frequency tripling of short-pulse
KrF laser radiation are presented. Argon gas is selected as nonlinear medium due to the resonantly enhanced 3rd-order susceptibility
χ(3)(-3ω,ω,ω,ω). Pulse energies of 100 μJ at 82.8 nm have been measured for a pump pulse energy of 14 mJ. An upscaling to more
than 500 μJ is expected with available more powerful pump lasers. Features of this XUV source and possible applications are
discussed.
Received: 26 July 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-511/7622211, E-mail: reinhardt@iqo.uni-hannover.de 相似文献
6.
A. Jurgilaitis R. Nüske H. Enquist H. Navirian P. Sondhauss J. Larsson 《Applied Physics A: Materials Science & Processing》2010,100(1):105-112
In this paper, we present the investigation and characterization of the laser-induced surface structure on an asymmetrically
cut InSb crystal. We describe diffraction from the ripple surface and present a theoretical model that can be used to simulate
X-ray energy scans. The asymmetrically cut InSb sample was irradiated with short-pulse radiation centred at 800 nm, with fluences
ranging from 10 to 80 mJ/cm2. The irradiated sample surface profile was investigated using optical and atomic force microscopy. We have investigated how
laser-induced ripples influence the possibility of studying repetitive melting of solids using X-ray diffraction. The main
effects arise from variations in local asymmetry angles, which reduce the attenuation length and increase the X-ray diffraction
efficiency. 相似文献
7.
Simone Pentzien Andrea Conradi Robert Koter J?rg Krüger 《Applied Physics A: Materials Science & Processing》2010,101(2):441-446
Cleaning of cultural assets, especially fragile organic materials like paper, is a part of the conservation process. Laser
radiation as a non-contact tool offers prospects for that purpose. For the studies presented here, paper model samples were
prepared using three different paper types (pure cellulose, rag paper, and wood-pulp paper). Pure cellulose serves as reference
material. Rag and wood-pulp paper represent essential characteristics of the basic materials of real-world artworks. The papers
were mechanically soiled employing pulverized charcoal. Pure and artificially soiled paper samples were treated with laser
pulses of 28 fs (800 nm wavelength) and 8–12 ns (532 nm) duration in a multi pulse approach. Additionally, the cellulose reference
material was processed with 30 ps (532 nm) laser pulses. Damage and cleaning thresholds of pure and soiled paper were determined
for the different laser regimes. Laser working ranges allowing for removal of contamination and avoiding permanent modification
to the substrate were found. The specimens prior and after laser illumination were characterized by light-optical microscopy
(OM) and scanning electron microscopy (SEM) as well as multi spectral imaging analysis. The work extends previous nanosecond
laser cleaning investigations on paper into the ultra-short pulse duration domain. 相似文献
8.
Mehdi Ranjbar Azam Iraji zad Seyyed Mohammad Mahdavi 《Applied Physics A: Materials Science & Processing》2008,92(3):627-634
In this study WO
x
films were deposited by laser ablation of ultra-pure (5N) tungsten trioxide targets onto SiO2 or silicon substrates at 250°C temperature, 100 mTorr oxygen partial pressure and 1×10−5 Torr vacuum. Surface chemical states and compositions of the deposits were determined by X-ray photoelectron spectroscopy.
The results showed that deposits in oxygen partial pressure contain W6+ with x∼3.1, while vacuum-deposited films have different W states with various percentage distributions as W4+>W5+>W6+>W0, and x∼1. We used fast electrical resistance measurement as a probe to study the deposition process. Film resistance as a function
of deposition time in vacuum revealed some microsecond fluctuations modulated on the time variation curve of electrical resistance.
We attribute these data to surface absorption and desorption of oxygen during layer deposition. Finally, the effect of the
laser beam on the target’s structure, surface morphology and chemical state was studied. Our results revealed that in spite
of structural variation by laser irradiation, the O/W ratio remained about 3. 相似文献
9.
Thorsten Ulm Florian Harth Harry Fuchs Johannes A. L’huillier Richard Wallenstein 《Applied physics. B, Lasers and optics》2008,92(4):481-485
This paper reports the generation of fs light pulses by a passively mode-locked InGaAs master oscillator power amplifier (MOPA)
system. The laser system generates chirped pulses with 6.2 ps duration, a center wavelength of 922 nm and 4 GHz repetition
rate. Pulse compression by an external grating compressor reduces the pulse duration to 580 fs. The average power of the compressed
pulses of 851 mW corresponds to a peak power of 366 W. 相似文献
10.
We demonstrate the control of neutral fragmentation of methane(CH4) induced by a Ti:sapphire intense laser pulse(800 nm, 40 fs) by using a pump–probe spectroscopy. Enhancement of the fluorescence emission from the neutral radical CH(A2Δ → X2Π) induced by the intense laser field(~1014 W/cm2) is observed when the wavelength of the probe laser pulse is tuned to 400 nm. The phenomena are explained based on excitation enhancement of the super-excited state of the parent molecule resulting in an increase in neutral dissociation of the methane molecules. 相似文献
11.
The ablation theory of cornea and biology effect by 193-nm ArF excimer laser are introduced. The ablation tracks model is put forward to make laser spots scan around cornea by many steps and many areas to change cornea curvature. The corneal average ablation curve is calculated by software so as to explain the feasibility of the ablation tracks model. By analyzing the actual ablation shapes of many arbitrary cornea sections, the optimal ablation method for deciding the random position of every laser spot in every ablation track is obtained. Experiments combining the ablation model with the device testify the energy stability of laser spots and the accuracy of rectifying anisometropia. 相似文献
12.
D. A. Zayarny A. A. Ionin S. I. Kudryashov S. V. Makarov A. A. Kuchmizhak O. B. Vitrik Yu. N. Kulchin 《JETP Letters》2016,103(12):752-755
Single-shot thresholds of surface ablation of aluminum and silicon via spallative ablation by infrared (IR) and visible ultrashort laser pulses of variable width τlas (0.2–12 ps) have been measured by optical microscopy. For increasing laser pulse width τlas < 3 ps, a drastic (threefold) drop of the ablation threshold of aluminum has been observed for visible pulses compared to an almost negligible threshold variation for IR pulses. In contrast, the ablation threshold in silicon increases threefold with increasing τlas for IR pulses, while the corresponding thresholds for visible pulses remained almost constant. In aluminum, such a width-dependent decrease in ablation thresholds has been related to strongly diminished temperature gradients for pulse widths exceeding the characteristic electron-phonon thermalization time. In silicon, the observed increase in ablation thresholds has been ascribed to two-photon IR excitation, while in the visible range linear absorption of the material results in almost constant thresholds. 相似文献
13.
14.
G. Paunescu G. Spindler W. Riede H. Schr?der A. Giesen 《Applied physics. B, Lasers and optics》2009,96(1):175-183
We report on experimental and numerical investigations of femtosecond pulse propagation locally disturbed by the turbulent
flow field of a hot-air blower. The experiments show that turbulence may shorten the collapse/filamentation distance and induce
the onset of multiple filaments. This is supported by numerical simulations indicating that the high spatial frequency part
of the turbulence spectrum plays a significant role. 相似文献
15.
E. Takahashi S. Kato Y. Matsumoto I. Okuda 《Applied physics. B, Lasers and optics》2010,98(2-3):501-505
External-laser-induced preionization of excimer lasers was investigated. A discharge XeF laser was preionized by two different UV lasers [a KrF laser (λ=249 nm) and an ArF laser (λ=193 nm)], and the improvements in performance of the XeF laser were compared. The XeF laser beam profiles were measured by an intensified CCD (ICCD) camera with temporal resolution of 10 ns. Striated XeF laser profiles were obtained with 249 nm laser preionization, whereas there was no striation in the profiles for 193 nm laser preionization. These striations originated from discharge in the XeF laser induced by laser preionization. The influence of excited rare-gas atoms on the discharge instability was examined. 相似文献
16.
P. E. Dyer C. D. Walton R. Zakaria 《Applied Physics A: Materials Science & Processing》2009,95(2):319-323
Conical structures formed in 157 nm laser-ablated polycarbonate exhibit a well-defined fringe structure with a period of a
few 100 nm surrounding the cone base. Experiments and modelling studies of the interference produced by these micro-conical
mirrors are shown to provide a means of measuring the spatial coherence of the highly multi-mode 157 nm laser. 相似文献
17.
Recently, angle-resolved photoelectron spectra have been measured by exposing negative F? ions to linearly or circularly polarized infrared femtosecond laser fields. We compare the experimental results with numerical calculations carried out in the framework of a Keldysh-type theory modified to account for both the time shape and the spatial inhomogeneity of the pulse. In order to account for the finite duration of the laser pulse, our results have been obtained through calculations of photodetachment probabilities. By using the saddle-point method it is possible to show that the transition amplitude may be written as a coherent sum of terms giving rise to interferences. This circumstance suggests that some particular features of the experimental results may be described in terms of quantum interferences in the time domain. 相似文献
18.
E. Schulz T. Binhammer D. S. Steingrube S. Rausch M. Kovacev U. Morgner 《Applied physics. B, Lasers and optics》2009,95(2):269-272
Sub-10-fs-pulses are generated by self-compression in a noble gas filament. Using input pulses from a Ti:sapphire amplifier
system with an energy of about 1.5 mJ at a repetition rate of 3 kHz and a pulse duration of 30 fs self-compressed sub-10-fs
pulses with energies of about 0.3 mJ have been generated. These pulses are characterized with spectral phase interferometry
for direct electrical-field reconstruction (SPIDER). Depending on the laser parameters, we observe a significant change in
the chirp of the white-light. The spectral distribution of the outcoming beam profile is measured to distinguish the white-light
core from the surrounding halo. 相似文献
19.
L. Chen B.-L. Pan Y.-J. Wang Q. Zhu X.-Y. Zhang 《Applied physics. B, Lasers and optics》2010,98(2-3):507-510
An experimental investigation on the characteristics of laser and current pulses in a He–SrCl2 vapor laser is carried out. The temporal dependences of the discharge current pulse on the laser pulses at the 1.09 μm, ~3 μm and 6.45 μm lines in strontium atoms and ions are measured and analyzed under different laser output powers. It is found that all laser pulses appear at the falling edge of the current pulse and shift forward to the current pulse with increasing laser output power. 相似文献
20.
P. Kumar 《Applied Physics A: Materials Science & Processing》2010,99(1):245-250
Controlled single step fabrication of silicon conical surface modulations on [311] silicon surface is reported utilizing KrF excimer laser [λ=248 nm] at laser fluence below ablation threshold laser fluence. When laser fluence was increased gradually from 0 to 0.2 J/cm2 for fixed 200 numbers of shots; first nanopores are observed to form at 0.1 J/cm2, then very shallow nanocones evolve as a function of laser fluence. At 0.2 J/cm2, nanoparticles are observed to form. Up to 0.15 J/cm2 the very shallow nanocone volume is smaller but increases at a fast rate with laser fluence thereafter. It is observed that the net material volume before and after the laser irradiation remains the same, a sign of the melting and resolidification without any ablation. 相似文献