Catálogo de publicaciones - libros

We show that different schemes can be now followed to produce collimated X-ray radiation using laser systems. By focusing intense femtosecond laser light onto a gas jet, electrons of the plasma can be manipulated to generate ultrafast (femtosecond) X-ray radiation in the forward direction along the laser axis. In this chapter we discuss nonlinear Thomson scattering, betatron emission and Compton scattering. In years to come, the rapid development of laser technology will provide more intense laser systems. We can expect to see the creation of bright X-ray beams with a high degree of collimation (< 1 mrad divergence), as well as even shorter pulse durations, down to attosecond time scales. Such sources will provide multidisciplinary scientific communities with unique tools to probe and excite matter.

Atomic clusters offer a unique area for studying high-intensity laser-matter interactions. When a high-intensity laser pulse interacts with a single cluster, the cluster absorbs most of the incident laser energy into its restricted small volume, producing a high-temperature “cluster plasma” which generates high-energy electrons and ions as well as bright X-rays. When a sufficiently short laser pulse is used, the laser energy is deposited before the cluster can expand, paving the way for developing laser-based debris-free ultrafast X-ray sources for time-resolved diffraction experiments. In this study, in order to understand a fundamental aspect of the laser-cluster interaction, we have carried out systematic investigations of the relativistic cluster plasmas, created by the action of superintense, ultrafast laser irradiation, by the simultaneous measurements of high-resolution X-ray emission spectra and ion energy spectra. It is found that hot electrons produced by a higher-contrast pulse shift the ion balance towards the higher charge states, which enhances both the X-ray line yield of the He-like argon ion and the ion kinetic energy.

Rapid progress in recent years in the development of high power ultra-short pulse laser systems has opened up a whole new vista of applications and computational challenges. New experimental developments in the field of extreme nonlinear optics will require more rigorous electromagnetic propagation models beyond those existing in the current literature. In this chapter, we derive a 3D time domain unidirectional vector Maxwell propagator that resolves the underlying optical carrier wave while allowing propagation over macroscopic many-meter distances. Our model allows for extreme focusing conditions down to the order of the wavelength in the material. A novel aspect of our approach is that the pulse propagator is designed to faithfully capture the light-material interaction over the broad spectral landscape of relevance to the interaction. Moreover the model provides a seamless and physically self-consistent means of deriving the many ultra-short pulse propagation equations presented in the literature. Amongst current applications that are most challenging from a computational point of view are those involving critical self-focusing with concomitant explosive growth in the generated light spectrum. Specific application areas chosen for illustration include multiple filament formation during propagation of ultra-intense femtosecond laser pulses in air and nonlinear self-trapping in condensed media. These examples exhibit rather different aspects of intense femtosecond pulse propagation and demonstrate the robustness and flexibility of our recently formulated unidirectional Maxwell propagator. A clear message to emerge from our study is the inadequacy of spectrally local light-material interaction models when nonlinear coupling exists over many hundreds of nanometer frequency bandwidths. More sophisticated, computationally feasible, models of nonlinear dispersion are needed.

When ultrashort (fs), high-power laser pulses propagate through the atmosphere, extended plasma filaments form and emit white light in a spectral range spanning from the ultraviolet (230 nm) to the infrared (4.5 µm). This strongly non-linear optical phenomenon results from a dynamical balance between respectively focusing and defocusing Kerr- and plasma-lenses, which are formed by a nonuniform, intensity-dependent refractive index across the laser beam profile. This non-linear propagation regime opens the way to various applications in atmospheric sciences, such as white-light Lidar relying on the white light continuum, which can be observed up to high altitudes and allows multicomponent remote sensing. Other applications rely on the ability of the filaments to deliver high-intensities and induce non-linear optical effects at remote locations, e.g. bioaerosols remote sensing or solid target analysis. Furthermore, the ionization of the fs-laser-induced filaments permits to control high-voltage discharges, opening the way to laser lightning rods. This chapter shall review the basic properties of filamentation, with a particular emphasis on one spectacular feature: Their ability to propagate unperturbed across clouds and fogs.

Filamentation is a non-linear propagation regime of ultrashort, high-power laser pulses, in which a dynamic balance is established between Kerr self-focusing and defocusing on the air ionized by the laser pulse itself. It opens the way to various applications in atmospheric sciences, such as white-light Lidar relying on the white light continuum, which can be observed up to high altitudes and allows multicomponent remote sensing. Other applications rely on the ability of the filaments to deliver high intensities and induce non-linear optical effects at remote locations, e.g. the remote sensing of aerosols or the analysis of solid targets. Furthermore, the ionization of the fs-laser-induced filaments permits to control high-voltage discharges, opening the way to laser lightning rods. These applications require a good characterization of filamentation over long distances in the atmosphere. This chapter reviews experimental results about long-range filamentation, the build-up of the white-light continuum and the beam geometry. Emphasis is put on results directly relevant for atmospheric applications.

Fast electrons are generated in the interaction between intense ultra-short laser pulses and the target. This interaction depends on the laser’s intensity, polarization, incident angle, the scale length of the plasma, and the target material. In this review, recent studies carried out at our laboratory on the dependence of the fast electrons on the experimental conditions of the laser and plasma as well as ways to control the fast electrons are presented.

Two laser-plasma processes among several others, namely the formation of relativistic electromagnetic solitons in warm plasmas and the ion acceleration driven by the interaction of ultraintense and ultrafast laser pulses with thin solid targets, have attracted great scientific interest in the last few years, both from a fundamental point of view and also in the light of the expected future technological applications. In this chapter, these two physical phenomena are presented and discussed, and the currently available theoretical descriptions are reviewed. Particular attention is paid to the analytical approaches, which allow to model the underlying physics in a transparent way and to give scaling laws with the laser and the plasma parameters. Emphasis is given to the discussion of the possible different regimes, which can characterize these processes, and to the identification of the most suitable theoretical treatments in the various cases.