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The post-compression technique based on self-phase modulation of high-energy pulses leads to an increase in achievable peak power and intensity. Typically, the pulses considered in experiments have been less than 100 fs in duration. Here, the method is applied to the ELFIE laser system at the LULI facility, for a pulse of 7 J energy and an initial measured duration of 350 fs. A 5-mm-thick fused silica window and a 2 mm cyclic-olefin polymer were used as optical nonlinear materials. The 9 cm diameter beam was spectrally broadened to a bandwidth corresponding to 124 fs Fourier-limited pulse duration, and then it was partly post-compressed to 200 fs. After measuring the spatial spectra of the beam fluence, a uniform gain factor of 4 increase in the fluctuations over the studied range of frequencies is observed, due to small-scale self-focusing. [ABSTRACT FROM AUTHOR]

Amplification of laser pulses based on the backscattering process in plasmas can be performed using either the response of an electron plasma wave or an ion-acoustic wave. However, if the pulse durations become very short and the natural spread in frequency a substantial amount of the frequency itself, the Raman and Brillouin processes start to mix. Kinetic simulations show the transition from a pure amplification regime, in this case strong-coupling Brillouin, to a regime where a considerable downshift of the frequency of the amplified pulse takes place. It is conjectured that in the case of very short pulses, multi-modes are excited which contribute to the amplification process. [ABSTRACT FROM AUTHOR]

This paper reviews the many recent advances at the Center for Ultrafast Optical Science (CUOS) at the University of Michigan in multi-MeV ion beam generation from the interaction of short laser pulses focused onto thin foil targets at intensities ranging from 1017 to 1019W/cm2. Ion beam characteristics were studied by changing the laser intensity, laser wavelength, target material, and by depositing a well-absorbed coating. We manipulated the proton beam divergence using shaped targets and observed nuclear transformation induced by high-energy protons and deuterons. Qualitative theoretical approaches and fully relativistic two-dimensional particle-in-cell simulations modeled energetic ion generation. Comparison with experiments sheds light on ion energy spectra for multi-species plasma, the dependences of ion-energy on preplasma scale length and solid density plasma thickness, and laser-triggered isotope yield. Theoretical predictions are also made with the aim of studying ion generation for high-power lasers with the energies expected in the near future, and for the relativistic intensity table-top laser, a prototype of which is already in operation at CUOS in the limits of several-cycle pulse duration and a single-wavelength spot size. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Discusses findings of a study of the deterministic character of optical damage by femtosecond laser pulses and applications to nanomachining. Challenge facing nanotechnology; Dynamics of optically induced dielectric breakdown; Damage threshold as a function of polarization.

The development of compact high-intensity lasers, made possible by the technique of chirped pulse amplification, is reviewed. This includes the complexities of high-power laser implementation, such as the generation of short pulses, pulse cleaning, wide-bandwidth amplification, temporal stretching and compression, and the requirements for high-average powers. Details of specific solid-state laser systems are given. Some applications of these lasers to short-pulse coherent short-wavelength [x-ray ultraviolet (XUV)] sources are also reviewed. This includes several nonlinear effects observed by focusing a subpicosecond laser into a gas; namely, an anomalous scaling of harmonic generation in atomic media, an upper limit on the conversion efficiency of relativistic harmonics in a plasma, and the observation of short-pulse self-focusing and multifoci formation. Finally, the effects of large ponderomotive pressures (100 Mbars) in short-pulse high-intensity laser-plasma interactions are discussed, with relevance both to recombination x-ray lasers and a novel method of igniting thermonuclear fusion. [ABSTRACT FROM AUTHOR]

Absorption and x-ray emission results obtained with a 1 psec pulse incident on solid targets with an intensity between 1011 and 1016 W/cm2 are presented and discussed. For I<5×1014 W/cm2, submicron density gradient scale lengths (L/λ≤0.2) are measured and the comparison of calculated and experimental values of absorption for aluminum indicates a relatively good agreement for p polarization and noticeable differences for s polarization. X-ray conversion efficiencies have been obtained in the sub-keV and keV range. At high intensities (I>1015 W/cm2) an evaluation of the plasma parameters is obtained from high resolution keV spectra. Finally, the results are discussed in the light of 1-D hydrodynamic simulations with time-dependent atomic physics. [ABSTRACT FROM AUTHOR]

Examines the laser-induced breakdown in fused silica with laser pulse widths from 7 nanosecond to 150 femtosecond. Measurement of the impact ionization coefficient; Role of photoionization in ultrashort pulses breakdown; Dominance of the avalanche ionization mechanism over the entire pulse-width range.

Plasma media, by exciting Raman (electron) or Brillouin (ion) waves, have been used to transfer energy from moderately long, high-energy light pulses to short ones. Using multidimensional kinetic simulations, we define here the optimum window in which a Brillouin scheme can be exploited for amplification and compression of short laser pulses over short distances to very high power. We also show that shaping the plasma allows for increasing the efficiency of the process while minimizing other unwanted plasma processes. Moreover, we show that, contrary to what was traditionally thought (i.e., using Brillouin in gases for nanosecond pulse compression), this scheme is able to amplify pulses of extremely short duration. [ABSTRACT FROM AUTHOR]