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Marc Sentis

Publications and source records attributed to Marc Sentis.

8 recordsLinked to original sources

Measurement of ultrashort laser ablation of four metals (Al, Cu, Ni, W) in single pulse regime

We provide measurements of ablation of four post-transition and transition metals (aluminum, copper, nickel and tungsten) irradiated by single 800 nm laser pulses, in ultrashort regime from 100 fs pulse duration down to 15 fs covering a temporal range little explored yet. For each metal and pulse duration tested, we measure its ablation characteristics (depth and diameter) as a function of incident energy allowing us to determine its laser-induced ablation threshold and ablation rate in single-shot regime. For all metals studied, we observe constant ablation threshold fluence as a function of pulse duration extending this scaling law to pulse duration of few-optical-cycles. We also provide evidence of the interest of adjusting the incident fluence to maximize the energy specific ablation depth but also of the absence of any peculiar advantage related to the use of extremely short pulse duration for ablation purposes. Those informative and detailed ablation data have been obtained in single pulse regime and in air ambiance. They can serve as rewarding feedback for further establishing smart strategy for femtosecond laser micromachining and laser damage handling of metallic and metal-based components as well as for enhancing accuracy of modeling of femtosecond laser interaction with metals in ultrashort regime.

physics.optics

Possible surface plasmon polariton excitation under femtosecond laser irradiation of silicon

The mechanisms of ripple formation on silicon surface by femtosecond laser pulses are investigated. We demonstrate the transient evolution of the density of the excited free-carriers. As a result, the experimental conditions required for the excitation of surface plasmon polaritons are revealed. The periods of the resulting structures are then investigated as a function of laser parameters, such as the angle of incidence, laser fluence, and polarization. The obtained dependencies provide a way of better control over the properties of the periodic structures induced by femtosecond laser on the surface of a semiconductor material.

cond-mat.mtrl-sci

Application of a two-temperature model for the investigation of the periodic structure formation on Si surface in femtosecond laser interaction

We consider the case of surface irradiation by a small number of femtosecond laser shots leading to the formation of surface ripples. To explain this effect, we propose a numerical model that accounts for the following processes: (i) interference of the laser irradiation with an electromagnetic surface wave propagating on a silicon sample; (ii) free carrier formation and laser energy absorption; (iii) energy relaxation and electron-phonon coupling. We perform numerical calculations taking into account the interference of a surface wave with laser; and present the obtained simulation results in order to explain formation mechanisms of the experimentally observed patterns.

physics.plasm-ph

Formation of femtosecond laser induced surface structures on silicon : insights from numerical modeling and single pulse experiments

Laser induced periodic surface structures (LIPSS) are formed by multiple irradiation of femtosecond laser on a silicon target. In this paper, we focus and discuss the surface plasmon polariton mechanism by an analysis of transient phase-matching conditions in Si on the basis of a single pulse experiment and numerical simulations. Two regimes of ripple formation mechanisms at low number of shots are identified and detailed. Correlation of numerical and experimental results is good.

physics.comp-ph

Interaction of UV photons with solid and nanocrystalline silicon

The studies of interaction of the UV photons with bulk and nanocristalline silicon by time-of-flight (TOF) mass-spectrometry allowed to reveal two populations of Si ion monomers. The first rapid population ejected even at low laser fluences is attributed to Colombian repulsion between the surface charges which are induced by emission of the photoelectrons. When the laser fluence increases, the second slow ion population appears. This population originates from the thermal processes in the irradiated material. The original result of this work is the observation of the non-thermal ion population which represents a considerable part of the laser-induced plume.

cond-mat.mtrl-sci

Enhancement of Exciton Emission from Zno Nanocrystalline Films by Pulsed Laser Annealing

Pulsed ArF laser annealing in air and in hydrogen atmosphere improves the optical properties of ZnO nanostructured films. Independently on the ambient atmosphere, laser annealing produces two major effects on the photoluminescence (PL) spectra: first, the efficiency of the exciton PL increases due to decrease of the number of non-radiative recombination centers; second, the intensity of the defect-related orange band decreases because of the removing of excessive oxygen trapped into the films during deposition. However, annealing in the ambient air also increases the intensity of the green band related to oxygen vacancies. We show that the combination of laser annealing and passivation of oxygen vacancies by hydrogen results in films free of defect-related emission and keeps intact their nanostructural character.

cond-mat.mtrl-sci

Synthesis and Laser Processing of ZnO Nanocrystalline Thin Films

We present the results of experiments on synthesis of ZnO nanoclusters by reactive pulsed laser deposition (PLD). The nanoclusters were formed and crystallized in the gas phase and deposited on SiO2 substrates. The nanostructured films were characterized by conventional photoluminescence (PL). The PL spectra consist of a narrow UV excitonic band and a broad visible band related to defects in the film. The film preparation conditions such as the substrate temperature, ambient gas nature and pressure, were optimized in order to increase the intensity of excitonic emission and prevent the formation of defects. A post-growth annealing by UV laser radiation improved the optical quality of the deposited films. The photoluminescence intensity was found to be dependent significantly on the laser fluence and on the number of shots per site. The nature of the defects responsible for the observed luminescence in a visible range is discussed.

cond-mat.mtrl-sci

Ablation de ZnO par laser UV (193 nm) : Nano-agregats en phase gazeuse

The condensation of zinc oxide nano clusters produced in gas phase has been evidenced in the ablation of a ZnO solid target by a pulsed ArF laser. We compare the spatio-temporal evolution of the shape of ZnO ablated plasma plume, both in vacuum and in controlled gas environments (Helium and/or Oxygen) from monitoring with CCD camera and from spectroscopic studies. The expansion of the plasma plume and the growth of the nanoclusters depend strongly upon the collisions between the ablated particles and surrounding gas molecules, as well as on the chemical reactions in the case of oxygen. The spectra of the observed plasma emittion are mainly due to atomic transitions in the neutral Zn. We have also observed the photoluminescence of the nanoclusters suspended in the gas and their decomposition in the beam of ArF laser.

physics.atm-clus