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The use of targets with surface structures for laser-driven particle acceleration has potential to significantly boost the particle and radiation energies because of enhanced laser absorption. We investigate, via experiment and particle-in-cell simulations, the impact of micron-scale surface-structured targets on the spectrum of electrons and protons accelerated by a picosecond laser pulse at relativistic intensity. Our results show that, compared with flat-surfaced targets, structures on this scale give rise to a significant enhancement in particle and radiation emission over a wide range of laser–target interaction parameters. This is due to the longer plasma scale length when using micro-structures on the target front surface. We do not observe an increase in the proton cutoff energy with our microstructured targets, and this is due to the large volume of the relief. [ABSTRACT FROM AUTHOR]

Advancement of ion acceleration by intense laser pulses is studied with ultra-thin nanometer-thick diamond like carbon and micrometer-thick Titanium target foils. Both investigations aim at optimizing the electron density distribution which is the key for efficient laser driven ion acceleration. While recently found maximum ion energies achieved with ultra-thin foils mark record values micrometer thick foils are flexible in terms of atomic constituents. Electron recirculation is one prerequisite for the validity of a very simple model that can approximate the dependence of ion energies of nanometer-thick targets when all electrons of the irradiated target area interact coherently with the laser pulse and Coherent Acceleration of Ions by Laser pulses (CAIL) becomes dominant. Complementary experiments, an analytical model and particle in cell computer simulations show, that with regard to ultra-short laser pulses (duration ~45 fs at intensities up to 5 × 1019 W/cm2) and a micrometer-thick target foil with higher atomic number a close to linear increase of ion energies manifests in a certain range of laser intensities. [ABSTRACT FROM PUBLISHER]

The results of experimental measurement and analytical estimation of the coefficient of backward reflection from targets made of various materials upon their irradiation by a picosecond laser pulse having the intensity of (0.8–4) × 1018 W/cm2 are presented. It is shown that the induced surface instability leads to the formation of a profile backscattering the incident radiation. The coefficient of backward reflection achieves a few percent and has an intensity optimum depending on the target material. [ABSTRACT FROM AUTHOR]

Spectra of intraband absorption of polarized mid-IR light were investigated in undoped, p-, and n-doped InAs/GaAs quantum dots (QDs) covered with an InGaAs layer. Optical matrix elements for intraband electron and hole transitions in QD5 have been calculated for different polarizations of light, and a good agreement with the experimental data is obtained. It is shown that the intraband absorption of light by electrons strongly exceeds the absorption by holes. Photoluminescence spectra and TEM images of structures with artificial molecules formed by pairs of QDs were studied. [ABSTRACT FROM AUTHOR]

The invention of high-power, ultra-short-pulse lasers has opened the way to investigations aimed at the creation of a new type of bright X-ray source for various uses including material science applications and time-resolved X-ray diffraction for biology. The efficiency with which laser energy incident on a solid target is converted into an X-ray emission depends on many factors, including the temporal profile of the laser pulse. Here we report the results of our theoretical and experimental investigations of the line X-ray emission from layered solid targets irradiated by ultra-short laser pulses. The laser prepulse parameters and target thickness are optimized to convert the maximum laser energy into an emission in the selected X-ray line. Multilayer foils are proposed to increase the energy of the Kα-line emission from laser plasma while simultaneously keeping the X-ray pulse duration at a hundred femtoseconds. The emission is studied both experimentally and theoretically by means of an analytical model and numerical simulations. [ABSTRACT FROM AUTHOR]

Abstract. Soft-X-radiation in the "water-window" region (23.3-43.6 Angstrom) mainly from carbon laser plasmas generated by subpicosecond (700 fs) 0.248-mu m laser pulses is studied as a function of angle of incidence and intensity (up to 10[sup 18] W/cm[sup 2]) for p-polarized laser light. Furthermore, comparison is made between plasmas generated from massive and toil targets. Numerical calculations are performed using a hydrocode coupled to X-ray line and continuum emission calculations including radiation transport. The optimized conditions to achieve maximum water-window X-ray emissivity and, in particular, carbon Lyman-alpha line emission are investigated. In addition, analytical scalings are presented. These theoretical results are essentially confirmed by previous experiments. It is found that at optimized conditions, picosecond or subpicosecond laser plasma X-ray sources with a power of the order of 1-10 GW in a spectral window of 1 Angstrom could be developed. [ABSTRACT FROM AUTHOR]