| 1. |
- Cantono, Giada, et al.
(författare)
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Laser-driven proton acceleration from ultrathin foils with nanoholes
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Structured solid targets are widely investigated to increase the energy absorption of high-power laser pulses so as to achieve efficient ion acceleration. Here we report the first experimental study of the maximum energy of proton beams accelerated from sub-micrometric foils perforated with holes of nanometric size. By showing the lack of energy enhancement in comparison to standard flat foils, our results suggest that the high contrast routinely achieved with a double plasma mirror does not prevent damaging of the nanostructures prior to the main interaction. Particle-in-cell simulations support that even a short scale length plasma, formed in the last hundreds of femtoseconds before the peak of an ultrashort laser pulse, fills the holes and hinders enhanced electron heating. Our findings reinforce the need for improved laser contrast, as well as for accurate control and diagnostics of on-target plasma formation.
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| 2. |
- Ferri, J., et al.
(författare)
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Enhancement of laser-driven ion acceleration in non-periodic nanostructured targets
- 2020
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Ingår i: Journal of Plasma Physics. - : Cambridge University Press (CUP). - 0022-3778 .- 1469-7807. ; 86:1
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Tidskriftsartikel (refereegranskat)abstract
- Using particle-in-cell simulations, we demonstrate an improvement of the target-normal-sheath acceleration (TNSA) of protons in non-periodically nanostructured targets with micron-scale thickness. Compared to standard flat foils, an increase in the proton cutoff energy by up to a factor of two is observed in foils coated with nanocones or perforated with nanoholes. The latter nano-perforated foils yield the highest enhancement, which we show to be robust over a broad range of foil thicknesses and hole diameters. The improvement of TNSA performance results from more efficient hot-electron generation, caused by a more complex laser-electron interaction geometry and increased effective interaction area and duration. We show that TNSA is optimized for a nanohole distribution of relatively low areal density and that is not required to be periodic, thus relaxing the manufacturing constraints.
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| 3. |
- Kaltenecker, K. J., et al.
(författare)
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Plasmonic Resonances Affecting Terahertz Generation in Laser-Induced Gas-Plasmas
- 2018
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - : Book Series: International Conference on Infrared Millimeter and Terahertz Waves. - 2162-2027 .- 2162-2035. ; 2018-September
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Konferensbidrag (refereegranskat)abstract
- We demonstrate that plasmonic resonances can be used to broaden the terahertz emission spectrum from two-color laser-driven gas-plasmas. This effect can be controlled by changing the polarization properties of elliptically shaped driving laser-pulses.
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| 4. |
- Migal, E. A., et al.
(författare)
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Role of deposited energy density and impact ionization in the processes of femtosecond laser-matter interaction in solids: scaling from visible to mid-IR
- 2019
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Ingår i: Nonlinear Optics and Applications XI. Proceedings Vol. 11026. SPIE OPTICS + OPTOELECTRONICS, 1-4 April 2019. - : SPIE. - 9781510627192
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Konferensbidrag (refereegranskat)abstract
- The deposited energy density (DED) serves as a key parameter in the process of the femtosecond laser pulse energy delivery into the bulk of transparent dielectrics. The laser-induced micromodification can be created if the value of DED exceeds a certain threshold, which is specific for each material and does not depend on the laser wavelength. In this contribution, we present a comprehensive study of the DED evolution with the driving pulse energy and wavelength under femtosecond microstructuring of transparent dielectrics. To precisely determine the laser impact area we applied for the first time a real-time diagnostic of microplasma based on third harmonic generation. This technique gives submicron spatial resolution and is extremely sensitive to the free electron density (about 10(-5) of the critical electron density). We found out that the threshold DED equals to approximately 2.5 kJ/cm(3) for fused silica and roughly corresponds to excess of glass transition temperature. The highest DED is achieved for the shortest wavelength (620 nm) and equals to 16 kJ/cm(3).
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| 5. |
- Petit, Y., et al.
(författare)
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Ultrashort laser induced spatial redistribution of silver species and nano-patterning of etching selectivity in silver-containing glasses
- 2019
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Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 27:10, s. 13675-13680
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Tidskriftsartikel (refereegranskat)abstract
- Femtosecond laser-induced spatial redistribution of silver species (ions, clusters. and hole centers) in a silver-containing phosphate glass is investigated by correlative means of near-field scanning optical microscopy (NSOM) images, numerical simulations, chemical micro-probe analysis. and nanoscale spatial profiles after soft etching. In particular, we found that the chemical etching selectivity for nanoscale patterning is strongly dependent upon the irradiation of femtosecond laser due to the spatial redistribution of silver species within the affected area. These results strongly indicate that controlling the distribution of silver species by femtosecond laser irradiation may open new routes for surface nanoscale chemical and/or spatial patterning for the fabrication of 2D surface photonic crystals. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 6. |
- Pineider, F., et al.
(författare)
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Plasmon-enhanced magneto-optical detection of single-molecule magnets
- 2019
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Ingår i: Materials Horizons. - : Royal Society of Chemistry (RSC). - 2051-6347 .- 2051-6355. ; 6:6, s. 1148-1155
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Tidskriftsartikel (refereegranskat)abstract
- Here we report on nanoarchitectures composed of molecular magnets deposited on optical nanoantennas. We demonstrate a significantly boosted magneto-optical detection of a thin film of a terbium(III) bis-phthalocianinato (TbPc2) single-molecule magnet and we track down the origin of this enhancement to nanoantenna effects at the optical level. This finding suggests that the vast knowledge on plasmon-enhanced spectroscopies can be readily extended to magneto-optics, thus paving the way to strong magneto-optical enhancements for the readout of nanometric devices embedding single-molecule magnets.
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| 7. |
- Potemkin, F. V., et al.
(författare)
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Influence of wave-front curvature on supercontinuum energy during filamentation of femtosecond laser pulses in water
- 2018
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 97:3
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that using spatially divergent incident femtosecond 1240-nm laser pulses in water leads to an efficient supercontinuum generation in filaments. Optimal conditions were found when the focal plane is placed 100-400 mu m before the water surface. Under sufficiently weak focusing conditions [numerical aperture (NA) < 0.2] and low-energy laser pulses, the supercontinuum energy generated in divergent beams is higher than the supercontinuum energy generated in convergent beams. Analysis by means of the unidirectional pulse propagation equation shows a dramatic difference between filamentation scenarios of divergent and convergent beams, that explains corresponding features of the supercontinuum generation. Under strong focusing conditions (NA >= 0.2) and high-energy laser pulses, the supercontinuum generation is suppressed for convergent beams in contrast to divergent beams that nevertheless are shown experimentally to allow supercontinuum generation. The presented technique of the supercontinuum generation in divergent beams in water is highly demanded in a development of femtosecond optical parametric amplifiers.
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| 8. |
- Smetanina, Evgeniya O., et al.
(författare)
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Optical Bloch modeling of femtosecond-laser-induced electron dynamics in dielectrics
- 2020
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Ingår i: Physical Review E. - 1539-3755. ; 101:6
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Tidskriftsartikel (refereegranskat)abstract
- A model based on optical Bloch equations is developed to describe the interaction of femtosecond laser pulses with dielectric solids, accounting for optical-cycle-resolved electron dynamics. It includes the main physical processes at play: photoionization, impact ionization, direct and collisional laser heating, and recombination. By using an electron band structure, this approach also accounts for material optical properties as nonlinear polarization response. Various studies are performed, shedding light on the contribution of various processes to the full electron dynamics depending on laser intensity and wavelength. In particular, the standard influence of the impact ionization process is retrieved.
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| 9. |
- Thiele, I., et al.
(författare)
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Terahertz emission from laser-driven gas plasmas: a plasmonic point of view
- 2018
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Ingår i: Optica. - : The Optical Society. - 2334-2536. ; 5:12, s. 1617-1622
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Tidskriftsartikel (refereegranskat)abstract
- We disclose an unanticipated link between plasmonics and nonlinear frequency down-conversion in laser-induced gasplasmas. For two-color femtosecond pump pulses, a plasmonic resonance is shown to broaden the terahertz emission spectra significantly. We identify the resonance as a leaky mode, which contributes to the emission spectra whenever electrons are excited along a direction where the plasma size is smaller than the plasma wavelength. As a direct consequence, such resonances can be controlled by changing the polarization properties of elliptically shaped driving laser pulses. Both experimental results and 3D Maxwell consistent simulations confirm that a significant terahertz pulse shortening and spectral broadening can be achieved by exploiting the transverse driving laser beam shape as an additional degree of freedom. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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