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This thesis describes pioneering research on the extension of plasmonics schemes to the regime of high-intensity lasers. By presenting a rich and balanced mix of experimentation, theory and simulation, it provides a comprehensive overview of the emerging field of high field plasmonics, including open issues and perspectives for future research. Combining specially designed targets and innovative materials with ultrashort, high-contrast laser pulses, the author experimentally demonstrates the effects of plasmon excitation on electron and ion emission. Lastly, the work investigates possible further developments with the help of numerical simulations, revealing the potential of plasmonics effects in the relativistic regime for advances in laser-driven sources of radiation, and for the manipulation of extreme light at the sub-micron scale.

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High Intensity Laser-Plasma Interaction and High Field Plasmonics.- Numerical Tools.- Electron Acceleration with Grating Targets.- Foam Targets for Enhanced Ion Acceleration.- Numerical Exploration of High Field Plasmonics in Di erent Scenarios.

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Luca Fedeli carried out his bachelor and master´s studies in physics at University of Milano-Bicocca (Italy), graduating in 2012 with a thesis on laser-induced shock-waves. From 2012 to 2015 he was a graduate student at University of Pisa, under the supervision of Dr A.Macchi (CNR/National Institute of Optics) and worked on various topics of high intensity laser plasma interaction and relativistic plasma phenomena. His research activity was mainly numerical (essentially Particle-In-Cell simulations), although he also took part in several experiments. In November 2015 he defended his PhD thesis on "High-field plasmonics". He is currently (2016) a post-doc at Politecnico di Milano (Italy).

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