[en] Nd:Glass amplifiers have very good energy storage capabilities (5 J/cm²), but, the energy extraction is extremely inefficient for short-pulse amplification. At relatively high peak intensities of ∼ 10 GW/cm², nonlinear phase shifts occur, leading to beam wavefront distortion which can result in filamentation and irreversible damage. In order that the peak intensity in the amplifier remain below this damage level, a picosecond pulse can be amplified only to an energy density of ∼ 10 mJ/cm², two orders of magnitude less than the stored energy level of 5 J/cm². We have developed an amplification system, which uses an optical pulse compression technique to circumvent this peak power limitation. This technique is analogous to a method developed over forty years ago for the amplification of radar pulses. Briefly: a long optical pulse is deliberately produced by stretching a short, low-energy pulse, amplified and then compressed. The frequency chirp and the temporal broadening are produced by propagating a high-intensity pulse along a single-mode fiber. At the beginning of the fiber, the pulse undergoes self-phase modulation which produces a frequncy chirp. The chirp is then linearized by the group-velocity dispersion of the fiber. This long, frequency-chirped, pulse is amplified, and then compressed to a pulsewidth approximately equal to 1/Δf, where Δf is the chirped bandwidth. With this system, short pulses can reach the high saturation energy levels, with moderately low peak power levels being maintained in the amplifying medium

No abstract available

[en] Lasers in the terawatt (TW) and peta-watt (PW) regime have the potential to replace conventional accelerators with the distinct advantage to be dramatically shorter by a factor of a thousand or more. For instance, electrons are accelerated to few GeV over only few centimeters, representing three to four orders of magnitude higher accelerating gradients than traditional RF-based accelerators can offer. Today, state-of-the-art high peak power laser system cannot pretend to be tomorrow's replacement to conventional RF Technology, a new class of ultrafast lasers is urgently needed. The following laser parameters are envisaged for what could be a future linear e"-e"+ collider: peak power in the PW regime, defined by a tenth of Joules of pulse energy and an ultrashort pulse duration below 50 fs, in combination with an unparalleled average power exceeding 100 kW even exceeding the megawatt level, implying repetition rates greater than 10 kHz. These extreme parameters should be contained in a beam of excellent spatial quality, featuring outstanding temporal stability and temporal contrast. (A.C.)

No abstract available

[en] Complete text of publication follows. ELI will be the first facility in the world dedicated to laser-matter interaction at unprecedented intensity levels. It will be also the first large scale infrastructure based in the eastern part of the European Community. It will explore ultrafast phenomena in the attosecond-zeptosecond domain and will be the gateway of a new regime in laser-matter interaction: the ultra relativistic regime that could reach into Nonlinear Quantum Electrodynamics, where vacuum polarization and elementary particle from vacuum can be produced. ELI's scientific mission will be a holistic investigation of the structure of matter, from atoms to vacuum. If the laser revolutionized atomic physics during the first fifty years, ELI in the same way could revolutionize nuclear physics. At the same time, it will also promote new technologies such as Relativistic Microelectronic with the development of compact laser-accelerators delivering very high-energy particles that could reach the 100 GeV level and photon sources in the MeV regime. ELI will have a large societal benefit offering in medicine new radiography and hadron therapy methods. It will also considerably contribute to material science with the possibility to unravel and slow down the aging process in nuclear reactor and in the environment by offering new ways of identifying radioactive elements.

[en] This article reviews the applications of ultra-intense lasers in domains like particle acceleration, gamma-gamma collisions, cancer diagnostic, eye surgery and inertial fusion. The main characteristic of such lasers is to deliver impulses carrying the same amount of energy as did previous generations of lasers but in a far shorter time which increases their power dramatically. Typically an ultra-intense laser releases 1 joule through an impulse that lasts 100 femtoseconds which means a power of 10¹³ Watt. The method of the amplification of impulses through frequency shift (CPA) has allowed power lasers to reach power levels that were beyond the technological limits of amplifying equipment (10⁹ W). The powerful electrical field of a femtosecond laser impulse make electrons oscillate with speeds nearing the speed of light while its magnetic field accelerates them in the perpendicular direction of the oscillation plane. Ultra-intense lasers generate electric fields from 10¹² to 10¹⁵ eV/m. (A.C.)

[en] The authors have directly observed the laser-induced melt metamorphosis of thin aluminum films. The time required for the melt to evolve is dependent on the degree to which the Al specimen is superheated. The temperature of this superheated state can also be monitored on the picosecond time scale. The picosecond electron probe not only reveals information about the structure of a material but also about the lattice temperature. The change in lattice parameter that is observed as a shift in diffracted ring diameter is directly related to the thermal expansion coefficient. Also, based on the Debye-Waller effect, a reduction in the intensity of the diffraction rings can be observed due to increased lattice vibration. Presently, a 1-kHz-1-mJ/pulse Nd:YAG laser is being used to measure the temperature overshoot of laser-induced Al films. The high repetition rate permits signal averaging to be employed thereby increasing the sensitivity of the thermometric technique

[en] A comparative analysis is performed of the electron emission characteristics as the electrons move in laser fields with ultra-relativistic intensity and different configurations corresponding to a plane or tightly focused wave. For a plane travelling wave, analytical expressions are derived for the emission characteristics, and it is shown that the angular distribution of the radiation intensity changes qualitatively even when the wave intensity is much less than that in the case of the radiation-dominated regime. An important conclusion is drawn that the electrons in a travelling wave tend to synchronised motion under the radiation reaction force. The characteristic features of the motion of electrons are found in a converging dipole wave, associated with the curvature of the phase front and nonuniformity of the field distribution. The values of the maximum achievable longitudinal momenta of electrons accelerated to the centre, as well as their distribution function are determined. The existence of quasi-periodic trajectories near the focal region of the dipole wave is shown, and the characteristics of the emission of both accelerated and oscillating electrons are analysed. (extreme light fields and their applications)

[en] Over 30 associated laboratories across 13 countries are part of the international program known as IZEST (International center for Zetta-Exawatt Science and Technology), which has been initiated and coordinated by the Polytechnique Graduate School and the CEA (French Commission for Atomic Energy and Alternative Energies). Together, this collaboration of laboratories are exploring new ways to push laser peak power and intensities beyond the present horizon with the aim to perform Laser-Based High Energy Physics. In this article the authors present the research directions by associating laser repetition rate with different regimes of luminosity including: -) the exploration of the low-luminosity regime with high energy lasers, -) the intermediate luminosity with moderately repetitive lasers, -) high luminosity regime with the coherent amplifying network (CAN) project. The application of IZEST laser technology to particle acceleration to 100 GeV and the search of dark fields are also presented

[en] Short pulses with ultrahigh peak powers have been generated in Nd: glass and Alexandrite using the Chirped Pulse Amplification (CPA) technique. This technique has been successful in producing picosecond terawatt pulses with a table-top laser system. In the near future, CPA will be applied to large laser systems such as NOVA to produce petawatt pulses (1 kJ in a 1 ps pulse) with focused intensities exceeding 10/sup /plus/21/ W/cm². These pulses will be associated with electric fields in excess of 100 e/a/sub o/² and blackbody energy densities equivalent to 3 /times/ 10¹⁰ J/cm³. This petawatt source will have important applications in x-ray laser research and will lead to fundamentally new experiments in atomic, nuclear, solid-state, plasma, and high-energy density physics. A review of present and future designs are discussed. 17 refs., 5 figs