共查询到20条相似文献,搜索用时 562 毫秒
1.
Alexander Horn Ilja Mingareev Alexander Werth Martin Kachel Udo Brenk 《Applied Physics A: Materials Science & Processing》2008,93(1):171-175
Using ultrafast laser radiation glass substrates are welded with glass and silicon plates. The pump beam is focused by a microscope
objective with large NA=0.4 (beam diameter 4 μm) into the glass. After partial absorption of the optical energy, the glass
is heated and melted. Procedures for high-quality welding of glass–glass and glass–silicon substrates with high-repetition
ultra-fast laser radiation have been derived at the repetition rate 700 kHz. The dependencies of the dimension and geometry
of the welding seam on scan velocity, repetition rate and pulse energy have been investigated defining a process window. Adding
a noninterferometric technique for quantitative phase detection with the welding setup, the interaction zone of the welding
seam for the welding partners glass–glass is detected. A change in refractive index is induced by heating and compression
of the glass and has been detected by phase detection up to 2 μs after irradiation with 100 fs time resolution. 相似文献
2.
Hirofumi Hidai David J. Hwang Costas P. Grigoropoulos 《Applied Physics A: Materials Science & Processing》2008,93(2):443-445
We demonstrate a new fiber growth mechanism in a photocurable resin by ultrafast laser illumination. A high-repetition rate
(∼1 MHz) ultrafast laser beam at the wavelength of ∼523 nm was focused into an ultraviolet photocurable resin to trigger two-photon
photopolymerization process. Time-resolved shadowgraphs and scattered light imaging revealed that the curing commenced in
the neighborhood of the geometric focal point of the laser beam and that the fiber growth progressed mostly towards the laser source. The cured fiber was thinner and longer than the profile of the focused laser beam, facilitated by nonlinear
propagation and absorption of the ultra-fast laser beam. The achieved aspect ratio of the fiber was higher than 180 with ∼10 μm
mean diameter, and the average growth rate was up to ∼2 mm/s. 相似文献
3.
Amin Abdolvand Robert W. Lloyd Marc J. J. Schmidt David J. Whitehead Zhu Liu Lin Li 《Applied Physics A: Materials Science & Processing》2009,95(2):447-452
We present results on the growth of highly organised, reproducible, periodic microstructure arrays on a stainless steel substrate
using multi-pulsed Nd:YAG (wavelength of 1064 nm, pulse duration of 7 ns, repetition rate of 25 kHz, beam quality factor of
M
2∼1.5) laser irradiation in standard atmospheric environment (room temperature and normal pressure) with laser spot diameter
of the target being ∼50 μm. The target surface was irradiated at laser fluence of ∼2.2 J/cm2 and intensity of ∼0.31×109 W/cm2, resulting in the controllable generation of arrays of microstructures with average periods ranging from ∼30 to ∼70 μm, depending
on the hatching overlap between the consecutive scans. The received tips of the structures were either below or at the level
of the original substrate surface, depending on the experimental conditions. The peculiarity of our work is on the utilised
approach for scanning the laser beam over the surface. A possible mechanism for the formation of the structures is proposed. 相似文献
4.
Robert Lloyd Amin Abdolvand Marc Schmidt Philip Crouse David Whitehead Zhu Liu Lin Li 《Applied Physics A: Materials Science & Processing》2008,93(1):117-122
Utilising a Nd:YVO4 laser (wavelength of 532 nm, pulse duration of 8 ns, repetition rate of 30 kHz) and a Nd:YAG laser (wavelength of 1064 nm,
pulse duration of 7 ns, repetition rate of 25 kHz), it was found that during the pulsed laser ablation of metal targets, such
as stainless steel, periodic nodular microstructures (microcones) with average periods ranging from ∼30 to ∼50 μm were formed.
This period depends on the number of accumulated laser pulses and is independent of the laser wavelength. It was found that
the formation of microcones could occur after as little as 1500 pulses/spot (a lower number than previously reported) are
fired onto a target surface location at laser fluence of ∼12 J/cm2, intensity of ∼1.5 GW/cm2. The initial feedback mechanism required for the formation of structures is attributed to the hydrodynamic instabilities
of the melt. In addition to this, it has been shown that the structures grow along the optical axis of the incoming laser
radiation. We demonstrate that highly regular structures can be produced at various angles, something not satisfactorily presented
on metallic surfaces previously. The affecting factors such as incident angle of the laser beam and the structures that can
be formed when varying the manner in which the laser beam is scanned over the target surface have also been investigated. 相似文献
5.
V. K. Rai 《Applied physics. B, Lasers and optics》2009,95(2):329-333
Upconversion luminescence in triply ionized praseodymium-doped TeO2–Li2O glass using excitation at ∼590 nm into the 1D2 level from a dye laser pumped with the second harmonic of a pulsed Nd:YAG laser has been reported. The mechanism involved
in the upconversion emission observed at ∼480 nm indicates that the most important contribution is energy transfer among praseodymium
ions in pairs followed by the dipole–dipole interaction. The rate-equation model for the emission at ∼480 nm that provides
direct information to determine the energy-transfer rates containing the pair of states involved in the upconversion process
has been explored. 相似文献
6.
G. P. Smith B. Krancevic D. L. Huestis H. Oser 《Applied physics. B, Lasers and optics》2009,94(1):127-132
Pulsed laser desorption of non-volatile organic dye molecules paraterphenyl and tetra-t-butyl-p-quinquephenyl (QUI) was studied
using gas phase ultraviolet laser induced fluorescence, following heating of a steel substrate by a pulsed 1.06-μm Nd:YAG laser. The fluorescence signal intensity is linear in concentration up to at least 30 monolayers and shows infrared
power threshold behavior, as expected for evaporation, at ∼0.2 J/cm2. Similar signal levels were also observed in air, with 532-nm heating, and using other metallic or dark black surfaces. 相似文献
7.
Yu. V. Volk A. M. Malyarevich K. V. Yumashev O. S. Dymshits A. V. Shashkin A. A. Zhilin 《Journal of Applied Spectroscopy》2007,74(1):140-146
We have studied the radiation output parameters for an erbium glass laser, lasing at a wavelength of 1.54 μm, with passive
Q-switching by means of a cobalt-containing magnesium aluminosilicate sitall compared with a saturable absorber based on a
magnesium aluminum spinel crystal with cobalt ions. We have shown that the output characteristics of the laser emission when
using sitall are not inferior to the analogous characteristics of a laser based on a spinel crystal, and are practically independent
of the temperature of the saturable absorber in the range 0°C–80°C. The duration (energy) of the output pulses was 70 nsec
(∼4 mJ), the energy dispersion of the radiation pulse relative to the average value was no greater than 3%, the beam divergence
was 2.8 mrad, the laser beam quality factor was M2 = 1.2.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 126–131, January–February, 2007. 相似文献
8.
H. Kim G. P. Kushto R. C. Y. Auyeung A. Piqué 《Applied Physics A: Materials Science & Processing》2008,93(2):521-526
Fluorine-doped tin oxide (FTO) thin films have been investigated as an alternative to indium tin oxide anodes in organic photovoltaic
devices. The structural, electrical, and optical properties of the FTO films grown by pulsed laser deposition were studied
as a function of oxygen deposition pressure. For 400 nm thick FTO films deposited at 300°C and 6.7 Pa of oxygen, an electrical
resistivity of 5×10−4 Ω-cm, sheet resistance of 12.5 Ω/□, average transmittance of 87% in the visible range, and optical band gap of 4.25 eV were obtained. Organic photovoltaic (OPV)
cells based on poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester bulk heterojunctions were prepared on FTO/glass electrodes and the device performance was investigated as a function of FTO
film thickness. OPV cells fabricated on the optimum FTO anodes (∼300–600 nm thick) exhibited power conversion efficiencies
of ∼3%, which is comparable to the same device made on commercial ITO/glass electrodes (3.4%). 相似文献
9.
Cumulative and continuous laser vaporization synthesis of single wall carbon nanotubes and nanohorns
A. A. Puretzky D. J. Styers-Barnett C. M. Rouleau H. Hu B. Zhao I. N. Ivanov D. B. Geohegan 《Applied Physics A: Materials Science & Processing》2008,93(4):849-855
The conditions for the scaled synthesis of single wall carbon nanotubes (SWNTs) and single wall carbon nanohorns (SWNHs) by
laser vaporization at high temperatures are investigated and compared using in situ diagnostics. An industrial Nd:YAG laser
(600 W, 1–500 Hz repetition rate) with tunable pulse widths (0.5–50 ms) is utilized to explore conditions for high-yield production.
High-speed videography (50000 frames/s) of the laser plume and pyrometry of the target surface are correlated with ex situ
high resolution transmission electron microscopy analysis of the products for pure carbon targets and carbon/catalyst targets
to understand the effects of the processing conditions on the resulting nanostructures. Carbon is shown to self-assemble into
single-wall nanohorn structures at rates of ∼1 nm/ms, which is comparable to the catalyst-assisted SWNT growth rates. Two
regimes of laser ablation, cumulative ablation by multiple pulses and continuous ablation by individual pulses, were explored. Cumulative ablation with spatially overlapping 0.5-ms pulses is favorable for
the high yield and production rate of SWNTs at ∼6 g/h while continuous ablation by individual long laser pulses (∼20 ms) at
high temperatures results in the highest yield of SWNHs at ∼10 g/h. Adjustment of the laser pulse width is shown to control
SWNH morphology. 相似文献
10.
Flame-generated soot was heated using a pulsed laser, and temperatures of the irradiated soot were inferred by fitting the
Planck function to spectrally resolved laser-induced incandescence with the temperature as an adjustable parameter. The effect
of the wavelength dependence of the emissivity on the inferred temperatures of the irradiated soot was studied using selected
expressions for the soot emissivity in the fit. Depending upon the choice of the functional form of the emissivity, the maximum
temperature reached by the soot during the laser pulse was calculated to span a range of 341 K (3475–3816 K) at a 1064-nm
laser fluence of 0.1 J/cm2 and 456 K (4115–4571 K) at a 1064-nm laser fluence of 0.4 J/cm2 with a 1σ standard deviation about the mean of ∼25 K. Comparison of the present results with temperature measurements from previous
studies suggests that the emissivity may depend on flame conditions and that further investigation on the subject is needed.
The use of two-color or spectrally resolved LII to infer the soot temperature during or after laser heating requires a careful
characterization of the wavelength dependence of the emissivity. The spread in temperature leads to large uncertainties regarding
the physico-chemical processes occurring at the surface of the soot during the laser heating. 相似文献
11.
12.
Spectroscopic concentration measurements of ammonia and ethylene were done with a pulsed, distributed feedback (DFB) quantum
cascade (QC) laser centered at 970 cm−1. An astigmatic Herriot cell with 150 m path length was employed, and we compare the results from experiments using inter-
and intrapulse techniques, respectively. The measurements include the detection of ammonia in breath with these methodologies.
In the interpulse technique, the laser was excited with short current pulses (5–10 ns), and the pulse amplitude was modulated
with an external current ramp resulting in a ∼0.3 cm−1 frequency scan. A standard amplitude demodulation technique was implemented for extracting the absorption line, thus avoiding
the need for a fast digitizer or a gated integrator. In the intrapulse technique, a linear frequency down-chirp is used for
sweeping across the absorption line. A 200 ns long current pulse was used for these measurements which resulted in a spectral
window of ∼1.74 cm−1 during the down-chirp. The use of a room temperature mercury-cadmium-telluride detector resulted in a completely cryogen
free spectrometer. We demonstrate detection limits of ∼3 ppb for ammonia and ∼5 ppb for ethylene with less than 10 s averaging
time with the intrapulse method and ∼4 ppb for ammonia and ∼7 ppb for ethylene with the interpulse technique with an integration
time of ∼5 s. 相似文献
13.
Optical waveguide fabrication and integration with a micro-mirror inside photosensitive glass by femtosecond laser direct writing 总被引:1,自引:0,他引:1
Z. Wang K. Sugioka Y. Hanada K. Midorikawa 《Applied Physics A: Materials Science & Processing》2007,88(4):699-704
Photosensitive glass is a potentially important material for micro-fluidic devices that can be integrated with micro-optical
components for biochemical analysis. Here, we demonstrate the fabrication of optical waveguides inside glass by femtosecond
laser direct writing. The influence of the laser parameters on the waveguide properties is investigated, and it is revealed
that the waveguide mode can be well controlled. The single mode is achieved at a low writing energy, while the multimode is
achieved with increasing energy. In spite of a longitudinally elongated elliptical shape of the cross-sectional profile, the
far-field pattern of the single-mode waveguide shows an almost symmetric profile. The measured propagation loss and the coupling
loss are evaluated to be ∼0.6 dB/cm and ∼1.6 dB at a wavelength of 632.8 nm, respectively, under the conditions of 1.0–2.0 μJ
pulse energy and 200–500 μm/s scan speed. The increased optical loss is associated with a higher waveguide mode at higher
writing energy. Furthermore, the integration of waveguides and a micromirror made of a hollow microplate inside the glass
is demonstrated to bend the laser beam at an angle of 90° in a small chip. The bending loss is estimated to be smaller than
0.3 dB.
PACS 42.62.-b; 42.82.Cr; 82.50.Pt; 42.79.Gn; 42.81.Qb 相似文献
14.
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
15.
P. Frank F. Lang M. Mosbacher J. Boneberg P. Leiderer 《Applied Physics A: Materials Science & Processing》2008,93(1):1-4
Steam Laser Cleaning with a pulsed infrared laser source is investigated. The infrared light is tuned to the absorption maximum
of water (λ=2.94 μm, 10 ns), whereas the substrates used are transparent (glass, silicon). Thus a thin liquid water layer condensed on
top of the contaminated substrate is rapidly heated. The pressure generated during the subsequent phase explosion generates
a cleaning force which exceeds the adhesion of the particles. We examine the cleaning threshold in single shot experiments
for particles sized from 1 μm down to 300 nm. 相似文献
16.
V. D. Zvorykin A. O. Levchenko A. G. Molchanov I. V. Smetanin N. N. Ustinovskii 《Bulletin of the Lebedev Physics Institute》2010,37(2):60-64
The grazing mode of microwave propagation in a hollow plasma waveguide formed by ionization of atmospheric air with a small
easily ionized additive by strong UV pulses of the Garpun KrF laser (λ = 248 nm, the pulse duration and energy are ∼70 ns and ∼50 J) was experimentally demonstrated for the first time. The annular
laser beam produced a hollow tube ∼10 cm in diameter with an electron density of ∼1012 cm−3 in a plasma wall ∼1 cm thick, over whichmicrowave radiation with λ
mw
∼ 8 mm was transmitted to a distance of 60 m. Themicrowave signal transmitted by the waveguide was amplified by a factor
of 6 in comparison with propagation in free space. 相似文献
17.
Surface nanostructuring of silicon 总被引:1,自引:0,他引:1
A.J. Pedraza J.D. Fowlkes Y.-F. Guan 《Applied Physics A: Materials Science & Processing》2003,77(2):277-284
Irradiation with polarized laser light of 248-nm wavelength induces the formation of periodic undulations ∼10-nm-highon flat
silicon substrates. The wavelength of these periodic structures is a function of the light wavelength and the angle of incidence
of the laser beam. Linear arrays of silicon nanoparticles with fairly uniform size that extended up to a millimeter were formed
if the irradiation was performed using polarized light. When non-polarized laser light with the same fluence was used to illuminate
an initially flat surface, non-aligned nanoparticle strings were obtained. However, if part of the irradiated area was microstructured,
nanoparticle linear arrays resulted in the vicinity of the microstructured region. An analysis on the evolution of these nanostructures
is presented. Nanocolumns could be grown on top of every cone of a microstructured surface upon cumulative laser irradiation
with non-polarized light, reaching a height of ∼3 μm and a diameter of 100–200 nm. The mechanisms of nanocolumn origin and
growth are analyzed.
Received: 16 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-865/974-4115, E-mail: apedraza@utk.edu 相似文献
18.
J. S. Yu S. Slivken A. Evans M. Razeghi 《Applied Physics A: Materials Science & Processing》2008,93(2):405-408
High-temperature, high-power, and continuous-wave (CW) operation of quantum-cascade lasers with 35 active/injector stages
at λ∼8.85 μm above room temperature is achieved without using a buried heterostructure. At this long wavelength, the use of a
wider ridge waveguide in an epilayer-down bonding scheme leads to a superior performance of the laser. For a high-reflectivity-coated
21 μm×3 mm laser, the output power of 237 mW and the threshold current density of 1.44 kA/cm2 at 298 K under CW mode are obtained with a maximum wall-plug efficiency of 1.7%. Further improvements were observed by using
a 4-mm-long cavity. The device exhibits 294 mW of output power at 298 K and it operates at a high temperature, even up to
358 K (85°C). The full widths at half-maximum of the laser beam in CW operation for the parallel and the perpendicular far-field
patterns are 25°and 63°, respectively. 相似文献
19.
N. A. Inogamov S. I. Ashitkov V. V. Zhakhovsky V. V. Shepelev V. A. Khokhlov P. S. Komarov M. B. Agranat S. I. Anisimov V. E. Fortov 《Applied Physics A: Materials Science & Processing》2010,101(1):1-5
Ultrashort laser pulse transfers metal into a two-temperature warm dense matter state and triggers a chain of hydrodynamic
and kinetic processes—melting, expansion, stretching, creation of tensile stress and transition into metastable state. We
study the response of aluminum film deposited on a glass substrate to irradiation by a pump laser pulse transmitted through
glass. Several films with thicknesses from 350 to 1200 nm have been investigated. The smallest thickness is of the order of
the heating depth d
T∼100 nm in Al. The d
T-layer and the free rear side of the film are coupled through pressure waves propagating between them. Therefore, the processes
within d
T-layer affects the time dependent displacement Δ
x
rear(t) of the rear surface. We compare simulated and experimental dependencies Δ
x
rear(t) obtained by the pump–probe technique. It allows us to define a thickness of molten Al layer and explore the two-temperature
processes occurring inside the heated layer. 相似文献
20.
I. Gallardo K. Hoffmann J. W. Keto 《Applied Physics A: Materials Science & Processing》2009,94(1):65-72
Laser Ablation of Microparticles (LAM) is a process of nanoparticle formation in which microparticles in a flowing aerosol
are continuously ablated by high-power laser pulses. For the first time, we have produced CdSe/ZnS core/shell nanoparticles
using a double ablation apparatus, designed to undergo a two-step LAM process. This process can be inverted to produce ZnS/CdSe
core/shell nanoparticles. The present work focuses on the range around ∼15 nm radius heterostructures and uses high-resolution
transmission electron microscopy (HRTEM) to image core and shells. For smaller particles, core shell structures have been
detected with energy dispersive spectroscopy (EDS) 5 nm spot size beam and fast Fourier transform (FFT) spectra. Differences
in the ablation behavior were measured between the two IIB–VIA type semiconductors. 相似文献