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Showing papers on "Fluence published in 1997"


Journal ArticleDOI
TL;DR: In this paper, the authors studied the ablation of metal targets by Ti:sapphire laser radiation and showed that the intensity depends logarithmically on the laser fluence.
Abstract: Ablation of metal targets by Ti:sapphire laser radiation is studied. The ablation depth per pulse is measured for laser pulse durations between 150 fs and 30 ps and fluences ranging from the ablation threshold ∼0.1 J/cm2 up to 10 J/cm2. Two different ablation regimes are observed for the first time. In both cases the ablation depth per pulse depends logarithmically on the laser fluence. A simple theoretical model for a qualitative description of the experimental results is presented.

914 citations


Journal ArticleDOI
TL;DR: In this paper, a finite element analysis was used to obtain the laser-induced densification independent of sample size, geometry, irradiation pattern, and intensity profile of the exposure beam, and the derived densification follows a universal function of the dose, defined as the product of the number of pulses and the square of the fluence per pulse.
Abstract: The experimental fact that fused silica undergoes densification upon prolonged exposure to high-energy radiation is well documented. About 25 years ago, Primak Kampwirth [J. Appl. Phys.39, 5651 (1968)] reported extensive densification results in SiO2 obtained with neutron, electron, and γ-ray exposures. More recently, results from experiments with pulsed deep-ultraviolet exposures have been reported. We report here our experimental results and analysis of the densification of Corning HPFS™ materials under 193-nm exposure. The densification δρ/ρ induced by the radiation was obtained from interferometric and birefringence measurements with the aid of a finite-element analysis. The use of such analysis is necessary to obtain the laser-induced densification independent of sample size, geometry, irradiation pattern, and intensity profile of the exposure beam. In our case the sample was 10 mm × 15 mm × 20 mm irradiated across the 10-mm face with a 5-mm apertured Gaussian beam in the 15-mm direction. The birefringence and wave-front distortion were measured off line as a function of number of pulses for distinct values of fluence per pulse. We found that the derived densification follows a universal function of the dose, defined as the product of the number of pulses and the square of the fluence per pulse. In fact, it follows the same functional form as that previously determined by Primak in his high-energy-exposure study. This strongly suggests that the laser-induced densification mechanism involves the optically induced weakening of bonds and subsequent relaxation.

104 citations


Journal ArticleDOI
TL;DR: In this article, the temperature and electron density of the plasma plumes produced by pulsed-laser ablation of aqueous solutions containing sodium, lithium, and rubidium were determined.
Abstract: We spectroscopically determined the temperature and electron density of the plasma plumes produced by pulsed-laser ablation of aqueous solutions containing sodium, lithium, and rubidium. With the use of a Nd:YAG laser at 532 nm and fluence of 3 J/cm2, the plasma produced was hot (low eV range) and extensively ionized, with electron density in the 1018 cm -3 range. Analyte line signals were initially masked by intense plasma continuum emissions and would only emerge briefly above the background when the plume temperature dropped below 1 eV during the course of its very rapid cooling. Since ionization was thermally induced, the intense plasma flash was inevitable. In contrast, 193-nm laser ablation at similar fluence generated plasmas of much lower ( < 1 eV) temperature but comparable electron density. Plasma continuum emissions were relatively weak, and the signal-to-background ratio was a thousand times better. Consequently, this ''cold'' plasma was ideal for sampling biologically important elements such as sodium, potassium, and calcium.

92 citations


Journal ArticleDOI
TL;DR: In this paper, an interpretation of the ion TOF distributions in terms of theoretical shifted Maxwell-Boltzmann distributions produces a good agreement with the experimental data, which has allowed us to infer the ion flow velocity and temperature associated with the measured TOF distribution, as well as the ion kinetic energies as a function of the laser fluence.
Abstract: ). The interpretation of the ion TOF distributions in terms of theoretical shifted Maxwell–Boltzmann distributions produces a good agreement with the experimental data. This has allowed us to infer the ion flow velocity and temperature associated with the measured TOF distributions, as well as the ion kinetic energies as a function of the laser fluence. We have also studied the total ion yield at different laser fluences. Our results show that all the plume parameters investigated are increasing functions of the laser fluence until a saturation plateau is reached at high fluences (>20 Jcm-2). We ascribe this saturation behav iour to strong absorption and partial, or total, reflection of the laser light by the hot plasma produced by the leading edge of the intense laser pulse. This interpretation is supported by a semi-quantitative analysis of the laser photon absorption and ionization mechanisms in Al plasma, at both laser wavelengths.

91 citations


Journal ArticleDOI
TL;DR: The minimum laser fluence required for the formation of ions from aerosol particles in a vacuum as a function of a number of parameters has been investigated in this paper, showing that the threshold energy density does depend on light absorption and lattice energy.
Abstract: The minimum laser fluence required for the formation of ions from aerosol particles in a vacuum as a function of a number of parameters has been investigated. Although the influences of various particle properties are complex, the threshold energy density does depend on light absorption and lattice energy. Ionization thresholds were lower at 193 and 157 nm than at 248 nm. The range in ion formation thresholds for different types of particles also decreased as the laser wavelength decreased, consistent with the fact that all the substances used are likely to absorb vacuum-ultraviolet radiation fairly strongly. The threshold for negative ion formation was generally greater than that for positive ion formation. Pure sulfuric acid aerosols were ionized well only at 157 nm.

80 citations


Journal ArticleDOI
TL;DR: In this article, a 300 keV, 30 kA, 1 μs intense beam of carbon, oxygen, and hydrogen ions is used for surface treatment of AISI-4620 steel coupons, a common material used in automotive gear applications.
Abstract: A 300 keV, 30 kA, 1 μs intense beam ofcarbon, oxygen, and hydrogen ions is used for the surface treatment of AISI-4620 steel coupons, a common material used in automotive gear applications. The beam is extracted from a magnetically-insulated vacuum diode and deposited into the top 1 μm of the target surface. The beam-solid interaction causes a rapid melt and resolidification with heating and cooling rates of up to 1010 K/s. Treated surfaces are smoothed over 1 μm-scale lengths, but are accompanied by 1 μm-diameter craters and larger-scale roughening over ≥ 10 μm, depending on beam fluence and number of pulses. Treated surfaces are up to 1.8 × harder with no discernible change in modulus over depths of 1 μm or more. Qualitative improvements in the wear morphology of treated surfaces are reported.

54 citations


Journal ArticleDOI
TL;DR: In this paper, laser hole drilling and polishing of CVD diamond (freestanding diamond and coated tool inserts) and HOPG (highly oriented pyrolytic graphite) using a 248 nm wavelength, 23 ns pulsed excimer laser were conducted.
Abstract: A laser beam offers the benefits of high precision, contamination-free, high speed, and low bulk temperature for machining of chemically vapour deposited (CVD) diamond thin films that in turn enable ultrafine finishing of diamond coated cutting tool inserts and drills, and for finishing and drilling of diamond coated multichip module applications. In this work, laser hole drilling and polishing of CVD diamond (free-standing diamond and coated tool inserts) and HOPG (highly oriented pyrolytic graphite) using a 248 nm wavelength, 23 ns pulsed excimer laser were conducted. The threshold energy fluence required for ablation of diamond and graphite was nearly the same but the material removal rate rapidly increases with the energy fluence for the graphite compared to diamond. At an energy fluence of 10 J cm-2, the depth removed per pulse was 0.05 μm and 0.30 μm for diamond and graphite respectively. Raman microprobe analysis indicates that the laser machining induced the transformation of diamond to disordered forms of carbon in CVD diamond and some transformation of graphite to diamond in HOPG. The experimental data indicates that the transformation of diamond to graphite requires an energy input of 1.44 × 107 J per mole. For a given set of laser parameters, the depth per pulse was substantially higher for diamond coated tool inserts compared to the free-standing diamond. The surface roughness of CVD diamond was reduced by 0.25 μm per pulse at an energy fluence of 16 J cm-2

49 citations


Journal ArticleDOI
TL;DR: It is shown that by using fluence modulation the influence of dose inhomogeneities can be significantly reduced and when two or more electron beam energies with individually optimized fluence profiles are used the dose conformality to the internal target volume is further increased, particularly for targets with complex shapes.
Abstract: The possibilities of using simultaneous fluence and energy modulation techniques in electron beam therapy to shape the dose distribution and almost eliminate the influences of tissue inhomogeneities have been investigated. By using a radiobiologically based optimization algorithm the radiobiological properties of the tissues can be taken into account when trying to find the best possible dose delivery. First water phantoms with differently shaped surfaces were used to study the effect of surface irregularities. We also studied water phantoms with internal inhomogeneities consisting of air or cortical bone. It was possible to improve substantially the dose distribution by fluence modulation in these cases. In addition to the fluence modulation the most suitable single electron energy in each case was also determined. Finally, the simultaneous use of several preselected electron beam energies was also tested, each with an individually optimized fluence profile. One to six electron energies were used, resulting in a slow improvement in complication-free cure with increasing number of beam energies. To apply these techniques to a more clinically relevant situation a post-operative breast cancer patient was studied. For simplicity this patient was treated with only one anterior beam portal to clearly illustrate the effect of inhomogeneities like bone and lung on the dose distribution. It is shown that by using fluence modulation the influence of dose inhomogeneities can be significantly reduced. When two or more electron beam energies with individually optimized fluence profiles are used the dose conformality to the internal target volume is further increased, particularly for targets with complex shapes.

42 citations


Journal ArticleDOI
TL;DR: In this article, photoluminescence decay curves and nanosecond time-gated spectra were measured from silicon implanted SiO2 layers after thermal annealing.
Abstract: Photoluminescence decay curves and nanosecond time-gated spectra were measured from silicon implanted SiO2 layers after thermal annealing. Different ion fluences and annealing times were tested. Three components emitting blue-green light with lifetimes of about 0.4, 2, and 10 ns were detected. The peak position of all components moves to longer wavelengths upon increasing the ion fluence. This short-wavelength emission seems to be related to the presence of extended defects acting as precursors of nanocrystals. A slower (microsecond) component, centered in the near infrared and attributed to nanocrystals, was also identified in the highest fluence implant considered (3×1017 cm−2).

42 citations


Journal ArticleDOI
TL;DR: In this paper, a partially chlorinated Si(111)-(7 × 7) surface was subjected to 193 nm excimer laser radiation, and the number of photoetched atoms per unit of illumination time was calculated.

37 citations


Journal ArticleDOI
TL;DR: In this paper, a dual rod laser vaporization source coupled to a fast flow reactor is developed for the study of bimetallic clusters and their reactions, where the beam from the laser is split and then focused onto each rod, allowing the mixing ratio within the cluster to vary by altering the laser fluence on each rod.
Abstract: Reactivities of bimetallic clusters can be controlled by varying their composition, making them potentially valuable as catalysts and for use in elucidating the reactivities of such subnanoscale surfaces. A dual rod laser vaporization source coupled to a fast flow reactor is developed for the study of bimetallic clusters and their reactions. In order to establish the versatility of the technique, the results of studies are presented in which Nb/Al clusters are formed in two plasmas induced by the second harmonic (532 nm photons) of a single Nd:YAG laser and then detected by a quadrupole mass spectrometer. The beam from the laser is split and then focused onto each rod, allowing the mixing ratio within the cluster to vary by altering the laser fluence on each rod. With a low fluence on the Nb rod and a high fluence on the Al rod, an Al rich cluster distribution is formed, NbAlm− (m=2–20), and Alm− (m=5–31). By increasing the fluence on the Nb rod and decreasing the fluence on the Al rod, a Nb rich cluster ...

Journal ArticleDOI
TL;DR: In this paper, the effects of swift heavy ions in bulk materials have been studied and some models, such as the thermal spike, have been developed in order to explain the observed phenomena, but some questions remain debatable, among which the following ones: i) What is the spatial extension of the huge energy deposited by the swift heavy ion on the target electrons? ii) Can we evidence a pressure effect in some materials due to the lattice temperature increase?
Abstract: The effects of swift heavy ions in bulk materials have now long been studied and some models — such as the thermal spike — have been developed in order to explain the observed phenomena. Nevertheless, some questions remain debatable, among which the following ones: i) What is the spatial extension of the huge energy deposited by the swift heavy ions on the target electrons? ii) Can we evidence a pressure effect in some materials due to the lattice temperature increase? In most cases, we are able to predict whether a bulk material may be sensitive or not to the electronic energy loss S e of the incident ion. According to the thermal spike, a given material could be all the more sensitive to S e as the energy density deposited on the electrons is high. Therefore, an interesting way to increase this energy density is to confine the electrons in small target grains (i.e. submicrometric grains). This work reports the first experimental results obtained on irradiated tin oxide (SnO 2 ) nanopowders. The same grains have been observed by TEM and HREM before and after lead ion irradiation at several fluences (from 0.3 to 7.5 × 10 12 Pb cm −2 ). A modification gradually appears as the fluence increases up to a critical fluence above which the grains split into nanodomains. A possible explanation is given through the thermal properties of SnO 2 .

Journal ArticleDOI
TL;DR: In this article, the optical gain of cubic GaN on GaAs(001) upon pulsed optical pumping at room temperature was investigated and the initial decay time of the transient surface emission drastically decreases with increasing excitation density, reaching a value as short as 20 ps at a fluence of 50 μJ cm−2.
Abstract: We investigate the transient surface emission and the optical gain of cubic GaN on GaAs(001) upon pulsed optical pumping at room temperature. The initial decay time of the transient surface emission drastically decreases with increasing excitation density, reaching a value as short as 20 ps at a fluence of 50 μJ cm−2. This rapid decay suggests the presence of laterally amplified spontaneous emission. In fact, gain-stripe measurements of the edge emission reveal an optical gain exceeding 100 cm−1 at a fluence of 20 μJ cm−2.

Journal ArticleDOI
TL;DR: In this article, optical emission spectra (OES) of the ablated species were recorded for different distances from the target, for various laser fluences and for several N2 pressures.
Abstract: To investigate the characteristics of the plasma plume created by reactive laser ablation (RLA) of graphite, optical emission spectra (OES) of the ablated species were recorded for different distances from the target, for various laser fluences and for several N2 pressures. The spectra were dominated by the molecular bands of C2 and CN radical: C2 Swan and CN violet spectral systems. From the molecular band intensities the rotational and vibrational temperatures of CN radicals were derived though there is not a significant dependence of the temperature with fluence, a strong increase of intensity can be observed with the increase of the laser fluence.

Journal ArticleDOI
TL;DR: UV-induced excess losses have been measured at various pulse energy densities and exposure times in germanosilicate optical fiber preform cores and the corresponding refractive-index changes have been determined through a Kramers -Kronig analysis.
Abstract: UV-induced excess losses have been measured at various pulse energy densities and exposure times in germanosilicate optical fiber preform cores. The corresponding refractive-index changes have been determined through a Kramers–Kronig analysis. Because of the nonlinear behavior of the excess losses as a function of both exposure time and fluence per pulse, one should be careful when comparing the refractive-index modulation deduced from such measurements with that obtained from Bragg grating reflectivity. Indeed nonlinear effects such as saturation imply that it is necessary to take into account the local character of the change in absorption to calculate the evolution of the refractive-index modulation accurately as a function of the exposure time. Implications of these results are discussed.

Journal ArticleDOI
TL;DR: In this article, the fraction of sp3 bonding in carbon thin film prepared using pulsed laser deposition with a KrF excimer laser is investigated, and it is suggested that the neutral species of C3 is effective in the formation of this structure.
Abstract: The fraction of sp3 bonding in carbon thin film prepared using pulsed laser deposition with a KrF excimer laser is investigated. The carbon film deposited at the laser fluence of 0.2 J/cm2 has a graphitic structure. It is suggested that the neutral species of C3 is effective in the formation of this structure. The C+ ion increases with a laser fluence higher than 0.9 J/cm2 and the sp3 bonding fraction in carbon film increases. The sp3 fraction in the film also increases with a negative bias to the substrate. The impact of energetic C+ species to the substrate is attributed to the formation of sp3 bonding.

Journal ArticleDOI
R. Aguiar1, V. Trtik1, Florencio Sánchez1, C. Ferrater1, Maria Varela1 
TL;DR: In this article, the laser wavelength has important effects on the crystalline properties of yttria stabilized zirconia (YSZ) films deposited on Si(100) by KrF and ArF excimer laser ablation.

Journal ArticleDOI
TL;DR: The surface structure and morphology of ion-beam irradiated 6FDA-pMDA films were investigated using atomic force microscopy (AFM) as mentioned in this paper, showing that small fluence irradiation induced microvoids in the surface layer of polyimide films.
Abstract: The surface structure and morphology of ion-beam irradiated 6FDA-pMDA films were investigated using atomic force microscopy (AFM) A beam of 140 keV N + ions with a low current density was used in this work Three irradiation fluences (2 x 10 14 /cm 2 , 1 x 10 15 /cm 2 , and 5 x 10 15 /cm 2 ) were chosen to represent three different regimes of ion-beam influence on material properties based upon previous diffusion and gas permeation results of implanted polyimide films Detailed roughness and bearing analyses of the AFM images indicate that freestanding polyimide films have deep surface valleys which can extend to a depth of several micrometers Ion-beam irradiation, even at a small dose, alters the microstructure of the surface layer and forms a modified layer which eliminates the initial deep valleys The AFM analysis shows that small fluence irradiation induced microvoids in the surface layer of the polymer, and high fluence irradiation resulted in a large number of small-size microvoids in the surface All of these results agree well with the ion-beam irradiation effects on iodine diffusion and gas permeation properties of the polyimides A ripple topographical structure with a wavelength of 25 μm and an amplitude of 2 nm was also observed for irradiated samples

Journal ArticleDOI
TL;DR: In this article, an anomalous degradation of short-circuit current density (Isc) was observed in a cell irradiated by energetic protons and electrons at high fluence, and the anomalous drop of Isc was caused by the p-type substrate changes into the intrinsiclike layer (Fermi level shift) by the irradiations, followed by an extension of the depletion layer.
Abstract: Distinct from the well-known logarithmic degradation in electrical performances of a crystalline silicon solar cell, an anomalous degradation of short-circuit current density (Isc) was observed in a cell irradiated by energetic protons and electrons at high fluence. From results of proton irradiations with various energies (0.4–10 MeV) and high frequency (1 MHz) capacitance measurements, the anomalous drop of Isc is found to be caused by (1) the p-type substrate changes into the intrinsiclike layer (Fermi level shift) by the irradiations, followed by an extension of the depletion layer, and (2) the drift length of the minority carrier becomes shorter than the depletion layer.

Journal ArticleDOI
TL;DR: In this article, a series of experimental studies on the radiation damage of UO2 was conducted by irradiation of high energy heavy ions in the order of 100 MeV, and the defect formation corresponding to the lattice parameter change was mainly due to nuclear energy deposition under the present experimental conditions, with an additional contribution of the electronic energy deposition.

Journal ArticleDOI
TL;DR: In this article, the positron lifetime spectroscopy combined with annealing experiments was used to study the vacancy production in 6H-SiC by 3 MeV electron irradiation at room temperature.
Abstract: The vacancy production in 6H-SiC by 3 MeV electron irradiation at room temperature was studied using positron lifetime spectroscopy combined with annealing experiments. It was found that the trapping rates of positrons in vacancies increased linearly with the fluence in the initial stage of irradiation. After the linear increase, the trapping rates were found to be proportional to the square root of the fluence. The linear and nonlinear fluence dependences of the trapping rates are explained by the reduction of vacancies due to recombination with interstitials during irradiation. The positron trapping rate for the admixture of silicon vacancies and divacancies showed a tendency to saturate in the higher fluence range. The trapping rate for carbon vacancies decreased after reaching a maximum. These results are explained in terms of the shift of the Fermi level due to the irradiation process. It was found that, for the lightly irradiated specimen, an annealing stage caused by recombination between close vacancies and interstitials was observed. However, such an annealing stage was not observed when using a heavily irradiated specimen. These different results are explained as the reduction of interstitials due to the recombination with vacancies and long-range migration of interstitials to sinks during irradiation.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrated that the peak cleaning force (per unit area) is larger than the adhesion force for submicron quartz particles on the NiP surface when it is irradiated by an excimer laser with a fluence above 10 mJ / cm 2.

Journal ArticleDOI
TL;DR: In this article, an easy model based on the hypothesis of thermal equilibrium between ejected vapour and heated surface, and of a local thermodynamic equilibrium state of the vapour, is used to characterize the metallic vapour at the end of the laser pulse.
Abstract: In this paper, the plasma ignition process above a metallic surface submitted to UV laser irradiation is studied. An easy model based on the hypothesis of thermal equilibrium between ejected vapour and heated surface, and of a local thermodynamic equilibrium state of the vapour, is used to characterize the metallic vapour at the end of the laser pulse. Then the efficiency of the different elementary mechanisms liable to sustain or to prevent the ionization process in this medium is discussed depending on the laser power density. In this work, the calculations are applied to the case of the interaction between an excimer XeCl laser beam ( nm, ns) and titanium target. It is shown that the thermal heated metallic vapour is partially ionized and contains excited and singly ionized species at high densities ( atoms ). The electron temperature in this medium is found to be around 1 eV. The study of the ionization rise in the vapour evidences the important role played by the single-photon ionization process and the electron/ion inverse bremsstrahlung effect. For laser power densities above 100 MW (laser fluence of 2 J cm), the ionization level is found to increase before the laser pulse end, and a thermal evaporation regime is reached. As the laser power density exceeds 500 MW (fluence of 10 J ), an avalanche breakdown is liable to occur in the vapour before the pulse end and the plasma governs the evaporation mode. The results presented here are in good agreement with experimental observations and with results from more complex models reported in the literature.

Journal ArticleDOI
TL;DR: In this paper, the authors calculated the fluence dependence of sputtering yield, retained fluence and nitrogen depth profiles as well as the implantation energy dependence of saturated thickness of a nitride layer by computer simulation using the dynamic SASAMAL code with various values of threshold displacement energy (Ed) and surface binding energy (Es).
Abstract: Nitrides are formed by high-fluence nitrogen implantation into various metallic targets, and their surface properties are improved. Among them, titanium nitride formation is of great interest in a wide range of technological applications. For nitrogen implantation into Ti with implantation energies of 10 keV to 1 MeV and fluences up to 1 × 1019 ions cm−2, the fluence dependence of sputtering yield, retained fluence and nitrogen depth profiles as well as the implantation energy dependence of saturated thickness of a nitride layer were calculated by computer simulation using the “dynamic SASAMAL” code with various values of threshold displacement energy (Ed) and surface binding energy (Es). The calculated results with Ed = 10 eV and Es = 1.6 eV for nitrogen agreed well with experimental values of the sputtering yield, the depth profile and the retained fluence of nitrogen obtained by Rutherford backscattering spectrometry and resonant nuclear reaction analysis for 50 keV nitrogen implantation at fluences of 6 × 1016 to 2 × 1018 ions cm−2. The thickness of the nitrogen-implanted layer saturated at high fluence and it was nearly equal to the sum of the mean projected range and the straggling value for all energies from 10 keV to 1 MeV.

Journal ArticleDOI
TL;DR: In this article, the authors used a YAG laser to ablate a high purity Al target in nitrogen reactive atmosphere, and X-ray diffraction studies revealed different crystalline orientation depending on deposition conditions: collectors temperature, position and orientation, reactive gas pressure, incident laser fluence.

Journal ArticleDOI
TL;DR: In this paper, the role of absorbing defects and their concentration as well as the influence on target roughness of places that absorb radiation more strongly than others are discussed. But the authors focus on simulations of the absorption of high fluence laser radiation by a target surface.

Journal ArticleDOI
TL;DR: In this paper, the energy loss function of ion beam irradiated polyimide has been deduced from optical and specular reflection in the range 2.5-6.5 eV.
Abstract: The energy loss function of ion beam irradiated polyimide has been deduced from optical and specular reflection in the range 2.5–6.5 eV. The appearance of a peak loss at 3 eV is the signature of the development of a sp 2 component responsible for optical gap narrowing and electronic conductivity. The different contributions to the photon energy loss function allowed the decomposition of the REELS (Reflection Energy Loss Spectroscopy) spectrum providing confirmation of a 3 eV component connected to the production of the conducting phase at high irradiation energy (170 keV Ne + ). The formation of this band is partially inhibited at low energy irradiation (50 keV Ne + ) as the proportion of nuclear transfers becomes significant. Rutherford Backscattering Spectrometry (RBS) shows that the diffusion of molecules can also be controlled by the irradiation modifications. Diffusion enhancement and gettering by the radiation damage is evidenced at low irradiation fluence. These modifications of the electronic and molecular transport properties are interpreted in relation with the irradiation induced nanostructure.

Journal ArticleDOI
TL;DR: In this article, a study of the time-integrated reflectivity of Al targets during laser-induced back ablation by 1064 nm, 10 ns laser pulses is reported.
Abstract: A study of the time-integrated reflectivity of Al targets during laser-induced back ablation by 1064 nm, 10 ns laser pulses is reported. The Al target reflectance data is analyzed using a model which includes not only Al surface removal but also the possible production of Al plasma. Calculations based on a sharp Al film ablation fluence (Jth≈710 mJ/cm2) threshold agree with the reflectance data. Plasma reflectance contribution is found to be negligible for plasma electron densities of less than 0.3 critical density.

Journal ArticleDOI
TL;DR: In this article, the amplitudes of acoustic waves depend on laser fluence, pulse number and surface condition of the substrate and can be used to determine the nature of laser-material interactions such as pulsed-laser-induced cleaning, surface roughening and ablation.

Journal ArticleDOI
TL;DR: In this paper, thin film samples of Kapton HF polyamide have been modified by UV-radiation using a pulsed excimer laser with per pulse fluences ranging from 29-50 mJ/cm 2.