共查询到20条相似文献,搜索用时 15 毫秒
1.
B.-Q. Yao X.-M. Duan L. Ke Y.-L. Ju Y.-Z. Wang G.-J. Zhao 《Applied physics. B, Lasers and optics》2010,98(2-3):311-315
We report continuous-wave (CW) and repetitively Q-switched operation of an in-band-pumped Ho:LuAG laser at room temperature. End-pumped by a Tm:YLF solid-state laser with emission wavelength of 1.91 μm, the CW Ho:LuAG laser generated 5.4-W output at 2100.7 nm with beam quality factor of M 2~1.03 for an incident pump power of 14.1 W, corresponding to slope efficiency of 67% with respect to absorbed pump power. Up to 1.5-mJ energy per pulse at pulse repetition frequency (PRF) of 3 kHz and 4.5-W average power with FWHM pulse width of 28 ns at 5 kHz were demonstrated in repetitively Q-switched operation. 相似文献
2.
Ablation process of 1-kHz femtosecond lasers (pulse duration of 148 fs, wavelength of 775 nm) of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D2 of the ablated craters and the laser fluence φ0. From the plot of the accumulated laser fluence Nφth(N) and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold axe in good agreement with the theoretical calculation. 相似文献
3.
Yudi Rosandi Herbert M. Urbassek 《Applied Physics A: Materials Science & Processing》2010,101(3):509-515
The optical properties of blue-violet InGaN light-emitting diodes under normal and reversed polarizations are numerically
studied. The best light-emitting performance under normal and reversed polarization is obtained in a single quantum-well structure
and double quantum-well structure, respectively. The key factors responsible for these phenomena are presumably the carrier
concentration distribution and the amount of carriers in quantum wells. The turn-on voltage of light-emitting diodes under
reversed polarization is lower than that of light-emitting diodes under normal polarization, due mainly to lower potential
heights for electrons and holes in the active region. 相似文献
4.
We analyze the morphology of ablated nanoparticles after their laser-induced deposition on various substrates. We show that, at moderate laser intensity of the 210 ps pulses on the surface of nanoparticle-containing materials (<5×109 W?cm?2), the deposited material remains approximately the same as the initial nanoparticles. We compare these deposited nanoparticles with the debris obtained by the laser ablation of bulk material of the same origin as nanoparticles at different intensities of laser radiation. The presence of nanoparticles in laser plumes allowed for analyzing high-order nonlinear optical properties of nanoparticles. The efficient high-order harmonic generation was achieved during propagation of femtosecond pulses through such plasmas. 相似文献
5.
S. I. Anisimov N. A. Inogamov Y. V. Petrov V. A. Khokhlov V. V. Zhakhovskii K. Nishihara M. B. Agranat S. I. Ashitkov P. S. Komarov 《Applied Physics A: Materials Science & Processing》2008,92(4):797-801
The mechanical action of laser exposure on a foil may result in the ablation of irradiated front layer and the rear-side spallation.
The dynamics of an Al foil is studied by means of two-temperature (2T) hydrodynamics and molecular dynamics (MD). It is found
that the rear-side spallation threshold F
s exceeds the front-side ablation threshold F
a. We propose to extend the common approach in laser-matter experiments by pump–probe measuring of the rear-side displacement. 相似文献
6.
S. Cockcroft C. D. Walton R. Zakaria 《Applied Physics A: Materials Science & Processing》2010,100(2):379-383
We report on the laser ablation of composite prismatic structures using a vacuum ultraviolet (VUV) 157 nm F2 laser. Polycarbonate and CR-39 substrates have been intentionally seeded with silver wires and silicon carbide whiskers respectively.
The seed particles remain attached to the underlying substrate after laser ablation, forming composite silver-polycarbonate
and silicon carbide-CR-39 interfaces. Strong optical absorption at 157 nm in the polymeric substrates allows precise control
over the depth between the base of the substrate and composite interface. The surface roughness of the as-received seed particles
has a significant effect on the final surface quality of the ablated structures. The textured surface on the silicon carbide
whiskers is resolved on the walls of the ablated structures. This is in contrast to the composite structures formed using
silver wires, which have a comparatively smoother surface. 相似文献
7.
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
8.
S. Lazare R. Bonneau S. Gaspard M. Oujja R. De Nalda M. Castillejo A. Sionkowska 《Applied Physics A: Materials Science & Processing》2009,94(4):719-729
Self standing films of biopolymers like gelatine, collagen, and chitosan irradiated with single nanosecond or femtosecond
laser pulse easily yield on their surface, a nanofoam layer, formed by a cavitation and bubble growth mechanism. The laser
foams have interesting properties that challenge the molecular features of the natural extracellular matrix and which make
them good candidates for fabrication of artificial matrix (having nanoscopic fibers, large availability of cell adhesion sites,
permeability to fluids due to the open cell structure). As part of the mechanistic study, the dynamics of the process has
been measured in the nanosecond timescale by recording the optical transmission of the films at 632.8 nm during and after
the foaming laser pulse. A rapid drop 100→0% taking place within the first 100 ns supports the cavitation mechanism as described
by the previous negative pressure wave model. As modeled a strong pressure rise (∼several thousands of bar) first takes place
in the absorption volume due to pressure confinement and finite sound velocity, and then upon relaxation after some delay
equal to the pressure transit time gives rise to a rarefaction wave (negative pressure) in which nucleation and bubble growth
are very fast. 相似文献
9.
S. Aggoune F. Vidal E. H. Amara 《Applied Physics A: Materials Science & Processing》2010,101(1):167-171
The interaction between a laser-produced aluminum plasma and the ambient air, at a pressure of 173.3 Pa, is studied at the
plasma thermalization stage. A two-dimensional approach is developed to solve the Navier–Stokes equations, where a finite
volume discretization allows for obtaining a numerical solution. The simulation runs over a time representing 10 μs of plasma
expansion. It is shown that the shock and drag models are good approximations for the two successive regimes after the initial
strong expansion stage, and the calculation makes evident the plume sharpening on the axial direction before its confinement
by the ambient gas, which is in good agreement with the experimental observation. 相似文献
10.
Y. P. Han J. L. Sun H. A. Ye W. Z. Wu G. Shi 《Applied physics. B, Lasers and optics》2009,94(2):233-237
In order to investigate the effect of pulse width and solvent on the nonlinear properties of metal nanostructures, silver
nanowires were fabricated in a direct current electric field (DCEF) using a solid-state ionic method and characterized by
transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nonlinear refractive index (γ) of silver nanowires suspended in ethanol was measured using the Z-scan technique and laser radiation of various (femto-,
pico-, and nanosecond) pulse durations. Experimental results indicated that silver nanowires have obvious positive refractive
nonlinearities and γ (the Kerr-induced self-focusing) increases as the pulse duration increases from 7.4×10−8 cm2/GW at 110 fs to 1.6×10−4 cm2/GW at 8 ns, due to the additional influence of the atomic reorientational Kerr effect in the case of longer pulses. Due to
the solvent dependence of the nonlinear behavior of the silver nanowires, the nonlinear absorption and refraction of silver
nanowires suspended in de-ionized water are smaller than those of silver samples suspended in ethanol. The thermal nonlinearities
are insignificant in our experimental conditions. 相似文献
11.
T. Kobayashi T. Kato Y. Matsuo M. Kurata-Nishimura Y. Hayashizaki J. Kawai 《Applied Physics A: Materials Science & Processing》2008,92(4):817-819
We investigate the so-called “matrix effect” on the relative intensities of ions in mixed solutions of alkali salts by using
femtosecond laser ablation time-of-flight mass spectrometry (fsLA-TOFMS). For the 1:1 mixed solution of sodium and potassium
salts, the intensity ratio of cations (Na+/K+) decreases as the total concentration increases. From the measurement for the mixed solution of lithium, sodium, potassium,
rubidium, and cesium solutions, we find out significant dependence of each ion intensity on the total concentration. The results
suggest that the electron transfer from neutral atoms to cations coexistent in the ablation plasma affects the relative ion
intensities observed with TOFMS when the total ion concentration is high. 相似文献
12.
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
13.
We show efficient generation of mid-IR pulses tunable between 1 and 5?μm from 100?kHz class femtosecond systems. The concept can be applied to various sources, particularly based on Ti:sapphire and the newly evolving Yb+ lasers. The mid-IR pulses are generated as the idler of a collinear optical parametric amplifier pumped by the laser fundamental. The seed for this amplifier is the idler of a previous amplification stage pumped with the second harmonic and seeded with a visible continuum. This enhances the energy and allows us to influence the bandwidth of the final output. Pulses with microjoule energy and Fourier limits of 50?fs are achieved. 相似文献
14.
From polymer films to organic nanoparticles suspensions by means of excimer laser ablation in water 总被引:1,自引:0,他引:1
I. Elaboudi S. Lazare C. Belin D. Talaga C. Labrugère 《Applied Physics A: Materials Science & Processing》2008,93(4):827-831
This study highlights the preparation of organic nanoparticles (NP) by laser ablation (LA) of polymeric materials in water.
Experiments focused on poly(ethylene terephtalate) (PET) were carried out with the KrF laser pulse (248 nm). Size distribution
and concentration of nanoparticles were deduced from suspensions turbidity measurements with the aid of Mie model, by Atomic
Force Microscopy (AFM) on the basis of a statistical study and Scanning Electron Microscopy (SEM). The obtained results show
that assemblies of spherical NP with a mean diameter 50 nm were synthesised. Composition and surface chemistry of NP were
investigated using the Confocal Micro-Raman Spectroscopy (CMRS) and X-ray Photoelectron Spectroscopy (XPS). It indicates that
NP are graphitic carbon rich and have a polymeric structure like polyacetylene. The possible mechanisms responsible of NP
synthesis by under water LA of polymers was briefly discussed by investigating other polymers targets. 相似文献
15.
E. P. Silaeva S. A. Shlenov V. P. Kandidov 《Applied physics. B, Lasers and optics》2010,101(1-2):393-401
The filamentation of a femtosecond laser pulse in atmosphere under the joint influence of turbulence and aerosol has been numerically studied for the first time. A result of these studies is that the presence of aerosol in a turbulent atmosphere increases the distance to the onset of multifilamentation. We have studied the competition between two factors of aerosol coherent scattering in the process of multiple filamentation of a femtosecond pulse in the atmosphere: generation of light field perturbations and energy losses. Similarity parameters have been determined for different conditions in the problem of multifilamentation in aerosol. 相似文献
16.
We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier. Groups of pulses with a temporal spacing of 10?ns and 1?kHz overall repetition rate are amplified to an average pulse energy of ~20?μJ and total burst energy of 0.25?mJ. The pulses are externally compressed to ~400?fs. The amplifier is synchronously pulsed-pumped to minimize amplified spontaneous emission between the bursts. We characterize the influence of pump pulse duration, pump-to-signal delay, and signal burst length. 相似文献
17.
Sachi Morinaga Takashi Nishiyama Takashi Kajiwara Kunihito Nagayama 《Applied Physics A: Materials Science & Processing》2010,101(4):743-746
A compositionally graded thin film of FeSi2 was fabricated by a gravity-assisted pulsed laser ablation (GAPLA) system. By this method, a compositionally graded structure
was successfully produced under a gravity field of 5400 G. We demonstrate that the atomic fraction of Fe, the heavier component
of the thin film measured by scanning electron microscope/energy dispersive X-ray (SEM-EDX), showed increasing spatial distribution
with the direction of gravity. We found that optimal laser fluence exists to give a thin film having the largest possible
spatial compositional gradient. We found that surface energy density on the substrate surface is the key parameter to control
the composition distribution. Furthermore, the ratio of Fe/Si of the film did not match that of the target. This result shows
that the Si component is selectively etched during the film-forming process. Relatively high laser fluence as well as a very
narrow space between the target and the substrate are essential to etch the film once it is deposited, in order to re-ionize
and etch Si selectively while gravity accelerates both Fe and Si particles to the direction of gravity. We hypothesize that
this process accounts for both the change in the stoichiometry and the formation of composition distribution. 相似文献
18.
N. Takada T. Nakano K. Sasaki 《Applied Physics A: Materials Science & Processing》2010,101(2):255-258
It is well known that a crater is formed on the target surface by the irradiation of intense laser pulses in laser ablation.
In this work, we report that additional pits are formed on the bottom surface of the ablation crater due to the collapse of
a cavitation bubble in liquid-phase laser ablation. We observed the formation of several cavitation-induced pits when the
fluence of the laser pulse used for ablation was approximately 5 J/cm2. The number of cavitation-induced pits decreased with the laser fluence, and we observed one or two cavitation-induced pits
when the laser fluence was higher than 10 J/cm2. In addition, we examined the influence of the liquid temperature on the formation of cavitation-induced pits. The collapse
of the cavitation bubble was not observed when the liquid temperature was close to the boiling temperature, and in this case,
we found no cavitation-induced pits on the bottom surface of the ablation crater. This experimental result was discussed by
considering the cavitation parameter. 相似文献
19.
L. Krainer R. Paschotta J. Aus der Au C. Hönninger U. Keller M. Moser D. Kopf K.J. Weingarten 《Applied physics. B, Lasers and optics》1999,69(3):245-247
We demonstrate passive mode locking of a Nd:vanadate (Nd:YVO4) laser to repetition rates of up to 13 GHz. With Ti:sapphire pumping, we achieved mode locking at 13 GHz with 310 mW of average
output power and pulse widths of 9.5 ps. With diode pumping, we achieved mode locking at a repetition rate of 12.6 GHz with
198 mW of average output power and a pulse duration of 8.3 ps.
Received: 6 July 1999 / Published online: 30 July 1999 相似文献
20.
《Current Applied Physics》2014,14(4):614-620
A high repetition rate (500 kHz) solid state laser was used for the ablation process in a Pulsed Laser Deposition (PLD)/Vapor–Liquid–Solid (VLS) growing. A ZnO target was ablated with laser powers between 0.6 W and 1.2 W, and a variable number of pulses per train and trains frequencies. ZnO structures were grown on gold patterned and unpatterned substrates surfaces. Enhanced growth of the nanostructures could be noticed on the catalyst patterned surfaces. Better nanowire morphologies were also observed for bigger number of laser pulses per train. The enhancements are more evident for low laser powers. Based on plume expansion investigations, by using a high speed camera and a Particle-In-Cell (PIC) Monte-Carlo based simulations, the nanostructure morphology variations could be understood on the basis of the plume particles diffusion process and thin film versus VLS growing competition. 相似文献