Oscillatory Langmuir probe ion current in laser-produced plasma expansion

Using the Langmuir probe method to investigate the parameters of laser-produced plasma, our experimental results show an oscillatory structure of the recorded transient ion current. The periodic behavior is analyzed for various targets and probe positions and, after extracting the continuous part, it is found to be connected with the ion frequency and the electron-ion collision frequency. We conclude that theories to describe these oscillations may provide new diagnostic techniques of laser-produced plasma

Influence of oxidation conditions on the properties of indium oxide thin films

cited By 49Indium oxide (In2O3) thin films have been prepared by thermal evaporation of indium in vacuum on a glass substrate at room temperature, followed by thermal oxidation in air. It was experimentally established that the heating velocity during the oxidation process has a strong influence on the electrical and optical properties of films as prepared. The temperature was increased from room temperature to 450 °C, with velocities ranging between 0.1 °C/s and 0.5 °C/s. In2O3 thin films as obtained have been examined for optical transparency function on wavelength. The calculated values of optical band gap range between 2.99 and 3.31 eV. Electrical conductivity measurements have also been carried out on the above oxide thin films as a function of temperature. Both the electrical and optical studies showed that In2O3 thin films with higher transparency and electrical conductivity are obtained at higher oxidation velocities. Also, the experimental results show linear dependences of transmission coefficient on the oxidation velocity

Fractal Transport Phenomena through the Scale Relativity Model

A correspondence between Nottale's scale relativity model and Cresson's mathematical procedures is analyzed. It results that the "synchronization" of the movements at different scales (fractal scale, differential scale etc.) gives conductive type properties to the fractal fluid, while the absence of "synchronization" is inducing properties of convective type. The behavior of a conductive fractal fluid is illustrated through the numerical simulation of plasma diffusion that is generated by laser ablation. Rotational and irrotational convective behaviors of a fractal fluid are established. Particularly, at Compton spatial and temporal scales, the irrotational behavior implies the standard Schrödinger equation

Laser ablation of AsxSe100-x chalcogenide glasses: Plume investigations

International audienceThe use of amorphous chalcogenides offers advantages such as remarkable optical properties like a wide transmission window (∼1-20 μm) depending upon composition, making them suitable for sensitive detection of clinical or environmental changes. They also present interesting high (non)linear refractive indices, photorefractive effects, and other properties interesting for wavelength conversion, all-optical switching or modulation, Raman and parametric amplification, laser sources for mid-IR, etc. Slab waveguides based on chalcogenide amorphous films with good adherence and controlled composition can be obtained using pulsed laser deposition allowing to design and to manufacture complex optical functions on waveguides within a small and compact chip. The aim of this work is to characterize the ejection plume obtained by laser ablation of AsxSe100−x samples in order to get some insight on the process involved for optimizing the pulsed laser deposition process. The dynamics of the plume has been systematically investigated by ICCD camera fast imaging and space- and time-resolved optical emission spectroscopy for samples of various compositions

Fractal Transport Phenomena through the Scale Relativity Model

A correspondence between Nottale's scale relativity model and Cresson's mathematical procedures is analyzed. It results that the "synchronization" of the movements at different scales (fractal scale, differential scale etc.) gives conductive type properties to the fractal fluid, while the absence of "synchronization" is inducing properties of convective type. The behavior of a conductive fractal fluid is illustrated through the numerical simulation of plasma diffusion that is generated by laser ablation. Rotational and irrotational convective behaviors of a fractal fluid are established. Particularly, at Compton spatial and temporal scales, the irrotational behavior implies the standard Schrödinger equation

Implications of an extended fractal hydrodynamic model

Considering that the motions of the particles take place on continuous but non-differentiable curves, i.e. on fractals with constant fractal dimension, an extended scale relativity model in its hydrodynamic version is built. In this approach, static (particle in a box and harmonic oscillator) and time-dependent (free particle etc.) systems are analyzed. The static systems can be associated with a coherent fractal fluid (of superconductor or of super-fluid types behavior), whose particles are moving on stationary trajectories. The complex speed field of the fractal fluid proves to be essential: the zero value of the real (differentiable) part specifies the coherence of the fractal fluid, while the non-zero value of the imaginary (non-differentiable or fractal) part selects, through some “quantization” relations, the “stationary” trajectories (that may correspond to the observables from quantum mechanics) of the fractal fluid particles. Moreover, the momentum transfer in the fractal fluid is achieved only through the fractal component of the complex speed field. The free time-dependent systems can be associated with an incoherent fractal fluid, and both the differentiable and fractal components of complex speed field are inhomogeneous in fractal coordinates due to the action of a fractal potential. It exist momentum transfer on both speed components and the “observable” in the form of an uniform motion is generated through a specific mechanism of “vacuum” polarization induced by the same fractal potential. The analysis on the fractal fluid specifies conductive properties in the case of movements synchronization both on differentiable and fractal scales, and convective properties in the absence of synchronization.

Experimental and theoretical aspects of aluminum expanding laser plasma

The formation and dynamics of aluminum laser produced plasma are experimentally and theoretically investigated. The visible emitting regions of plasma form two structures of different expansion velocities. Such behavior is in agreement with the transient current recorded by a cylindrical Langmuir probe. Using the hydrodynamic model of scale relativity theory, the plasma dynamics at different time scales are numerically and analytically analyzed. © 2009 The Japan Society of Applied Physics

Laser energy deposition on BN and SiO2 : experiment and model

Communication orale (C.Focsa)International audienc

Pulsed laser deposition of rare-​earth-​doped gallium lanthanum sulphide chalcogenide glass thin films

International audienceAmorphous chalcogenide thin films are of high current interest for technol. applications as optical storage media or waveguides for photonic integrated circuits. As part of a larger project including fs, ps and ns pulsed laser deposition regimes, Er- and Pr-​doped GLS thin films were deposited by ns PLD, and their structural, chem. and optical properties were analyzed by optical and electronic microscopy, stylus profilometry, X-​ray diffraction, Raman spectroscopy, time-​of-​flight secondary ion mass spectrometry (TOF-​SIMS)​, energy-​dispersive X-​ray spectroscopy, variable-​angle spectroscopic ellipsometry and optical transmission. Films deposited at moderate fluence (∼4 J​/cm2) in UV (266 nm) presented a good surface quality, while exhibiting acceptable compn. uniformity and deviations from stoichiometry in line with the literature. Compn. and optical properties dependences on the deposition conditions were investigated and discussed with respect to previous studies on similar systems