Marklund, M., Sergeev, A. (2011) Ultrarelativistic nanoplasmonics as a route towards extreme-intensity attosecond pulses.Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 84(4) The generation of ultrastrong attosecond pulses through laser-plasma interactions offers the opportunity to surpass the intensity of any known laboratory radiation source, giving rise to new experimental possibilities, such as quantum electrodynamical tests and matter probing at extremely short scales. Here we demonstrate that a laser irradiated plasma surface can act as an efficient converter from the femto-to the attosecond range, giving a dramatic rise in pulse intensity. Although seemingly similar schemes have been described in the literature, the present setup differs significantly from the previous attempts. We present a model describing the nonlinear process of relativistic laser-plasma interaction. This model, which is applicable to a multitude of phenomena, is shown to be in excellent agreement with particle-in-cell simulations. The model makes it possible to determine a parameter region where the energy conversion from the femto-to the attosecond regime is maximal. Based on the study we propose a concept of laser pulse interaction with a target having a groove-shaped surface, which opens up the potential to exceed an intensity level of 10 26 W/cm 2 and observe effects due to nonlinear quantum electrodynamics with upcoming laser sources.

A novel explanation of the relativistic self-induced transparency effect during superintense laser interaction with an overdense plasma is proposed. We studied it analytically and verified with direct modeling by both PIC and kinetic equation simulations. Based on this treatment, a method of ultrashort high-energy electron bunch generation with durations on a femtosecond time scale is also proposed and studied via numerical simulation.PACS numbers: 52.40. Nk, 52.35.Mw, 52.60.+h Recent progress in laser technology has paved the way of exploring previously unattainable regimes of ultraintense laser-plasma interaction [1]. In up-to-date experiments, laser intensities of the order of 10 21 W/cm 2 and higher can now be achieved, implying that the goals like the fast ignition concept for inertial confinement fusion (ICF) [2], laser-plasma based accelerators of charged particles [3,4], and compact sources of short-pulse x-ray radiation [5] might soon be within reach. It seems that this is exactly where fundamental physics and technological progress intersect. Here we address the fundamental issue of ultraintense electromagnetic (EM) wave propagation through classically overdense plasmas, namely, why it occurs in the regime of relativistic self-induced transparency (SIT). In fact, this regime was first considered in the pioneer work [6] in the form of stationary plane wave solution and later, in the 1970's, the stationary solutions were extended to non-homogeneous plasmas [7,8]. Recently, another type of solution was found indicating that an ultraintense EM wave can penetrate into overdense plasmas over a finite length only, forming structured plasma distributions as a sequence of electron layers separated by about half a wavelength wide depleted regions, so that this strongly nonlinear plasma structure acts as a distributed Bragg reflector [9]. However, such analytical studies, done in a rather academic manner, do not provide an answer of how and why the propagation of a laser pulse into overdense plasma occurs. Numerical simulations of ultraintense laser interaction with overdense plasmas, on the one hand, have confirmed that the SIT effect takes place but also have revealed additional effects like anomalous longitudinal electron heating, which can change the optical properties of the plasma and strongly influence pulse propagation dynamics [10,11,12,13,14,15]. Nevertheless, the fundamental question of the SIT regime -why the penetration into classically overdense plasma in the form of traveling wave occurs still has no reasonable explanation, especially taking into account strong peaking in the electron density in the front of the laser due to the ponderomotive force pushing electrons forward [16]. It is generally recognized that the penetration occurs through lowering of the effective dielectric constant due to relativistic electron mass correction and plasma heating up to relativistic temperatures under the action of laser field.In this Letter, in order to get an insight into the physics we focus special attenti...

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High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the target surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~10 5 T at laser intensities ~10 21 W cm –2 ) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire.