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1.
L. Egerhazi Zs. Geretovszky T. Szorenyi 《Applied Physics A: Materials Science & Processing》2008,93(3):789-793
Since the advent of pulsed laser deposition (PLD), several different target-substrate arrangements have been proposed. Besides
the most common on-axis PLD, several off-axis geometries were studied, mainly to protect the substrate from the agglomerated
species (clusters, droplets, particulates) of the plasma plume, which are detrimental to the homogeneity of films. Recently
we introduced a novel geometry, termed inverse pulsed laser deposition (IPLD), in which the substrate is placed parallel to
and slightly above the target plane. In this paper we summarize our results on this new geometry, and show how it can extend
the perspectives of pulsed laser deposition, e.g., by improving the surface morphology of the films. Effects of ambient pressure
are presented and exemplified on metallic and compound IPLD films, including Ti, CN
x
, and Ti-oxides. AFM topographic images are used to prove that under optimized conditions IPLD is capable of growing compact
and smooth films that are superior to PLD ones. A special—but easy-to-implement—IPLD arrangement is also introduced that considerably
improves the homogeneity of IPLD films. In this geometry, the properties (e.g., deposition rate and roughness) of the films
grown in the 1–25 Pa pressure domain are examined. 相似文献
2.
A compact battery-operated Nd-YAG laser is described which is capable of giving a free-running output energy of over 0.5 J. The device is capable of making small welds and of punching small holes in metal foil. Constructional details, a circuit diagram and operating data are given. 相似文献
3.
We predict the existence of a new pulsed-laser operation regime, when the phases and polarizations of the two coupled cold-cavity eigenstates of a monomode solid-state laser are taken into account in the derivation of the Maxwell-Bloch equations. This monomode pulsed regime is experimentally observed, without any normal mode locking or Q switching occurring inside the cavity. We obtain close agreement between experiments and theory, even in the simple case of a Nd:YAG microchip laser, for which sech(2) pulses at nearly megahertz repetition rates are readily observed. 相似文献
4.
An injection-locked pulsed Ti:sapphire laser oscillating at dual wavelengths is demonstrated for the first time to our knowledge. By use of two feedback loops, seeds of two independent master lasers are locked on specific longitudinal modes of a power oscillator, leading to a stable dual-wavelength oscillation over a long time scale. The two injection-locked pulsed outputs completely overlap in time, with spectral purities reaching a Fourier-transform limit. The dual-wavelength oscillation is controlled by the master lasers only, allowing for flexible selectivity of the two wavelengths and full controllability of the relative two-wavelength pulsed energies. 相似文献
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7.
P.J.M. Peters 《Optics Communications》1978,25(2):241-243
In this paper a simple sealed-off TEA CO laser is described with a self-sustained discharge without an external UV preionization source. At 77 K this system yields more than 600 mJ from a lasing volume of about 60 cm3 CO-N2-He mixture (45 J/? atm. with 15.6% efficiency). 相似文献
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9.
A compact self-seeded pulsed tunable laser is described. Its optical cavity comprises a diffraction grating, operating at
a grazing angle of incidence as a spectral selector and narrow-band spectral gate. The grating couples two partially overlapping
laser channels: a highly selective master laser and a nonselective slave laser. Due to the implemented efficient intracavity
self-seeding the laser emits spectrally pure single-longitudinal-mode radiation at two independently tunable wavelengths,
with an efficiency and output energy that are typical for nonselective lasers. Results of the experimental investigation of
the laser’s output characteristics are presented.
Received: 12 March 2001 / Revised version: 10 December 2001 / Published online: 7 February 2002 相似文献
10.
A new mechanism of pulsed laser oscillation based on ion-ion recombination is proposed. The advantages of utilizing this mechanism in a pulsed mode are considered, and the expected characteristics of the proposed lasers are estimated. 相似文献
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12.
Sucharita Sinha 《Applied Physics A: Materials Science & Processing》2013,112(4):855-862
A thermal model to describe high-power nanosecond pulsed laser ablation of yttria (Y2O3) has been developed. This model simulates ablation of material occurring primarily through vaporization and also accounts for attenuation of the incident laser beam in the evolving vapor plume. Theoretical estimates of process features such as time evolution of target temperature distribution, melt depth and ablation rate and their dependence on laser parameters particularly for laser fluences in the range of 6 to 30 J/cm2 are investigated. Calculated maximum surface temperatures when compared with the estimated critical temperature for yttria indicate absence of explosive boiling at typical laser fluxes of 10 to 30 J/cm2. Material ejection in large fragments associated with explosive boiling of the target needs to be avoided when depositing thin films via the pulsed laser deposition (PLD) technique as it leads to coatings with high residual porosity and poor compaction restricting the protective quality of such corrosion-resistant yttria coatings. Our model calculations facilitate proper selection of laser parameters to be employed for deposition of PLD yttria corrosion-resistive coatings. Such coatings have been found to be highly effective in handling and containment of liquid uranium. 相似文献
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This work investigates evaporation kinetics -- the relation between the surface temperature and pressure during excimer laser ablation. Nickel targets are ablated by excimer laser pulses in a laser fluence range between 1 and 6 J/cm2, with the upper limit exceeding the threshold of phase explosion (5 J/cm2). The surface pressure is determined with a polyvinylidene fluoride (PVDF) piezoelectric transducer. When phase explosion occurs, the surface temperature is known to be near the thermodynamic critical temperature, therefore, by measuring the surface pressure, the surface temperature-pressure relation is determined at the threshold fluence of phase explosion. The surface temperature and the threshold fluence of phase explosion are also estimated from the measured velocity of the vapor plume and gas dynamics calculations. It is shown that, during excimer laser ablation, the temperature and pressure relation deviates significantly from the equilibrium kinetic relation. 相似文献
15.
Theoretical analysis of the influence of the temporal profile (rectangular, triangular, Gaussian) of the laser pulse on heating/cooling and phase transition velocities and quantity of ablated material was performed on the basis of a multifront Stephan problem. Modeling showed that material removal under stationary conditions (that correspond to long pulses) is entirely controlled by specific heat and material density, while in the case of transient regimes (short pulses) thermal conductivity and heat capacity play a predominant role. Interaction of the melting and evaporation fronts characterized by an evaporation front velocity far exceeding the melting front one is one of the examples of the transient nature of the phenomena influenced by the laser pulse parameters. 相似文献
16.
Single-frequency high-energy Yb-doped pulsed all-fiber laser 总被引:1,自引:0,他引:1
A single-frequency pulsed all-fiber laser with a master oscillator power amplifier configuration is presented. While maintaining the properties of single mode, linear polarization, and narrow linewidth, a single-pulse energy of 260 μJ and over 500-W peak power is experimentally demonstrated at 1 kHz by employing tensile strain gradient and pulse-shape control methods. In addition, approximately 55 dB of optical signal to noise ratio is also achieved. 相似文献
17.
We show that a simple model for pulsed laser deposition exhibits an unusual type of scaling behavior for the island density in the submonolayer regime. This quantity is studied as a function of pulse intensity and deposition time. We find a data collapse for the ratios of the logarithms of these quantities, whereas conventional scaling as observed in molecular beam epitaxy involves ratios of powers. 相似文献
18.
Calculations of coherent picosecond pulse propagation in the free-electron laser are presented, based on a theory directly coupling the Maxwell and single-particle equations. Good agreement is obtained with data of the Stanford experiment, such as the power-tuning curve and the electron energy distribution. 相似文献
19.
In this study, the vibration phenomenon during pulsed laser forming of thin metal plates was investigated numerically and experimentally. The metal plates were made of 304 stainless steel and were heated by a CO2 Gaussian laser beam with a long pulse duration of 0.1 s, which incited vibration due to the elastic–plastic deformation of the specimen. This uncoupled thermal–mechanical problem was solved using a three-dimensional finite element method and was subsequently satisfactorily verified with experiments. Using the superposition method with multiple laser pulses, the non-linear vibration phenomenon during pulsed laser forming has also been observed experimentally for thin plates. 相似文献
20.
In the present paper, polyimide surfaces were processed with pulsed KrF laser radiation at fluences near the ablation threshold.
The morphology of the processed surfaces was studied by scanning electron microscopy and chemical analyses performed by electron
dispersive spectroscopy. The formation of conical structures was observed for radiation fluences lower than 0.5 J/cm2. The areal density of cones increases with the number of pulses and decreases with the radiation fluence. At low fluences
(<150 J/cm2), cones are formed due to shadowing by calcium phosphate impurities while for higher fluences the main mechanism of cones
formation is believed to be radiation hardening. 相似文献