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Corsi C.,European Laboratory for Non linear Spectroscopy LENS | Liontos I.,European Laboratory for Non linear Spectroscopy LENS | Liontos I.,Center for Plasma Physics and Lasers | Cavalieri S.,European Laboratory for Non linear Spectroscopy LENS | And 7 more authors.
Optics Express | Year: 2015

We developed an ultra-stable and accurately-controllable Michelson interferometer to be used in a deeply unbalanced arm configuration for split-pulse XUV Ramsey-type spectroscopy with high-order laser harmonics. The implemented active and passive stabilization systems allow one to reach instabilities in the nanometer range over meters of relative optical path differences. Producing precisely delayed pairs of pump pulses will generate XUV harmonic pulses that may significantly improve the achievable spectral resolution and the precision of absolute frequency measurements in the XUV. © 2015 Optical Society of America. Source


Lagomarsino S.,National Institute of Nuclear Physics, Italy | Lagomarsino S.,University of Florence | Bellini M.,CNR Institute of Applied Physics Nello Carrara | Bellini M.,CNR Institute of Neuroscience | And 12 more authors.
Diamond and Related Materials | Year: 2014

Pulsed laser writing of graphitic electrodes in diamond is a promising technique for innovative particle detectors. Although of great relevance in 3D fabrication, the processes involved in sub-bandgap bulk irradiation are still not well understood. In this work, Raman imaging is exploited to correlate resistivity and graphitic content in 5-10 μm-thick electrodes, obtained both in the domains of femtoseconds and of nanoseconds of pulse duration. A wide interval of resistivities (60-900 mΩcm), according to the irradiation technique employed, are correlated with an sp2 content of the modified material ranging over a factor 2.5. The stress distribution (maximum of about 10 GPa) and the presence of nanostructured sp3 material around the graphitic columns have also been studied by Raman spectroscopy, and a rationale for the conductive behavior of the material is presented in terms of the thermodynamics of the process. © 2014 Elsevier B.V. All rights reserved. Source


Brenner C.M.,University of Strathclyde | Brenner C.M.,Rutherford Appleton Laboratory | Robinson A.P.L.,Rutherford Appleton Laboratory | Markey K.,Rutherford Appleton Laboratory | And 24 more authors.
Applied Physics Letters | Year: 2014

An all-optical approach to laser-proton acceleration enhancement is investigated using the simplest of target designs to demonstrate application-relevant levels of energy conversion efficiency between laser and protons. Controlled deposition of laser energy, in the form of a double-pulse temporal envelope, is investigated in combination with thin foil targets in which recirculation of laser-accelerated electrons can lead to optimal conditions for coupling laser drive energy into the proton beam. This approach is shown to deliver a substantial enhancement in the coupling of laser energy to 5-30 MeV protons, compared to single pulse irradiation, reaching a record high 15% conversion efficiency with a temporal separation of 1 ps between the two pulses and a 5 μm-thick Au foil. A 1D simulation code is used to support and explain the origin of the observation of an optimum pulse separation of ∼1 ps. © 2014 Author(s). Source


Orphanos Y.,Center for Plasma Physics and Lasers | Orphanos Y.,Technological Educational Institute of Crete | Orphanos Y.,University of Patras | Dimitriou V.,Center for Plasma Physics and Lasers | And 11 more authors.
Microelectronic Engineering | Year: 2013

A novel integrated method enabling the study of nano-structured materials is presented, which is based on the imaging and monitoring of the spatiotemporal evolution of short-pulse-laser-generated Surface Acoustic Waves (SAWs). The method combines a 3D whole-field imaging laser interferometric experimental diagnostic technique and Finite Element Analysis (FEA) theoretical simulations. The experimental technique utilizes a single-longitudinal mode nanosecond laser source for both the generation and recording of the SAWs. It provides nanometer transverse spatial resolution vertical to the material surface, via direct whole-field imaging with nanosecond temporal resolution, thus avoiding extensive surface scanning. The theoretical model simulates the laser-material interaction as well as the generation and propagation of SAWs. FEA offers substantial insights into the materials' micro-elastomechanic behavior providing detailed information for the spatiotemporal evolution of SAWs. This integrated method is here applied on simple material samples consisted of thin metal films coated on dielectric substrates. The results validate the applicability and the potential of the proposed method in the area of nanostructured materials micromechanical characterization. © 2013 Elsevier B.V. All rights reserved. Source


Benis E.P.,University of Ioannina | Bakarezos M.,Center for Plasma Physics and Lasers | Papadogiannis N.A.,Center for Plasma Physics and Lasers | Tatarakis M.,Center for Plasma Physics and Lasers | And 3 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

Molecular hydrogen ion (H 2 +) dissociation paths of bond softening (BS) and above threshold dissociation (ATD) are investigated exploiting few-cycle chirped laser pulses. 7-fs laser pulses are temporally broadened in a controlled way by the imposed positive chirp covering the range 7-55 fs. The dissociation of the H 2 + molecules via the BS and ATD paths is then systematically monitored as a function of the pulses duration in conditions of equal H 2 + yield. The experimental data show distinctive characteristics both in the energy dissociation spectral structure as well as in the yield as the pulse duration broadens. The interpretation of our experimental findings is supported by ab initio calculations based on the H 2 + dissociation time-dependent Schrödinger equation (TDSE) in a strong laser field, thus shedding light into the details of the underlying dissociation dynamics involving few-cycle pulses. The results are also analyzed within the Floquet picture discussing certain limits of its applicability. Finally, our experimental findings show strong molecular alignment for durations longer than 20 fs. © 2012 American Physical Society. Source

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