Experimental evidence of short light pulse amplification using strong-coupling stimulated brillouin scattering in the pump depletion regime.

The energy transfer from a long (3.5 ps) pump pulse to a short (400 fs) seed pulse due to stimulated Brillouin backscattering in the strong-coupling regime is investigated. The two pulses, both at the same wavelength of 1.057 microm are quasicounterpropagating in a preformed underdense plasma. Relative amplification factors for the seed pulse of up to 32 are obtained. The maximum obtained amplified energy is 60 mJ. Simulations are in agreement with the experimental results and suggest paths for further improvement of the amplification scheme.

Picosecond short-range disordering in isochorically heated aluminum at solid density.

Using ultrafast x-ray probing, we experimentally observed a progressive loss of ordering within solid-density aluminum as the temperature raises from 300 K to >10{4} K. The Al sample was isochorically heated by a short ( approximately ps), laser-accelerated proton beam and probed by a short broadband x-ray source around the Al K edge. The loss of short-range ordering is detected through the progressive smoothing of the time-resolved x-ray absorption near-edge spectroscopy (XANES) structure. The results are compared with two different theoretical models of warm dense matter and allow us to put an upper bound on the onset of ion lattice disorder within the heated solid-density medium of approximately 10 ps.

Hot electrons transverse refluxing in ultraintense laser-solid interactions.

We have analyzed the coupling of ultraintense lasers (at ∼2×10{19} W/cm{2}) with solid foils of limited transverse extent (∼10 s of µm) by monitoring the electrons and ions emitted from the target. We observe that reducing the target surface area allows electrons at the target surface to be reflected from the target edges during or shortly after the laser pulse. This transverse refluxing can maintain a hotter, denser and more homogeneous electron sheath around the target for a longer time. Consequently, when transverse refluxing takes places within the acceleration time of associated ions, we observe increased maximum proton energies (up to threefold), increased laser-to-ion conversion efficiency (up to a factor 30), and reduced divergence which bodes well for a number of applications.

Absolute calibration of photostimulable image plate detectors used as (0.5-20 MeV) high-energy proton detectors.

In this paper, the absolute calibration of photostimulable image plates (IPs) used as proton detectors is presented. The calibration is performed in a wide range of proton energies (0.5-20 MeV) by exposing simultaneously the IP and calibrated detectors (radiochromic films and solid state detector CR39) to a source of broadband laser-accelerated protons, which are spectrally resolved. The final result is a calibration curve that enables retrieving the proton number from the IP signal.

Statistics of vector Manakov rogue waves.

We present a statistical analysis based on the height and return-time probabilities of high-amplitude wave events in both focusing and defocusing Manakov systems. We find that analytical rational or semirational solutions, associated with extreme, rogue wave (RW) structures, are the leading high-amplitude events in this system. We define the thresholds for classifying an extreme wave event as a RW. Our results indicate that there is a strong relationship between the type of RW and the mechanism which is responsible for its creation. Initially, high-amplitude events originate from modulation instability. Upon subsequent evolution, the interaction among these events prevails as the mechanism for RW creation. We suggest a strategy for confirming the basic properties of different extreme events. This involves the definition of proper statistical measures at each stage of the RW dynamics. Our results point to the need for redefining criteria for identifying RW events.

Influence of disorder on generation and probability of extreme events in Salerno lattices.

Extreme events (EEs) in nonlinear and/or disordered one-dimensional photonic lattice systems described by the Salerno model with on-site disorder are studied. The goal is to explain particular properties of these phenomena, essentially related to localization of light in the presence of nonlinear and/or nonlocal couplings in the considered systems. Combining statistical and nonlinear dynamical methods and measures developed in the framework of the theory of localization phenomena in disordered and nonlinear systems, particularities of EEs are qualitatively clarified. Findings presented here indicate that the best environment for EEs' creation are disordered near-integrable Salerno lattices. In addition, it is been shown that the leading role in the generation and dynamical properties of EEs in the considered model is played by modulation instability, i.e., by nonlinearities in the system, although EEs can be induced in linear lattices with on-site disorder too.

Hot and cold electron dynamics following high-intensity laser matter interaction.

The characteristics of fast electrons laser accelerated from solids and expanding into a vacuum from the rear target surface have been measured via optical probe reflectometry. This allows access to the time- and space-resolved dynamics of the fast electron density and temperature and of the energy partition into bulk (cold) electrons. In particular, it is found that the density of the hot electrons on the target rear surface is bell shaped, and that their mean energy at the same location is radially homogeneous and decreases with the target thickness.