Towards optical polarization control of laser-driven proton acceleration in foils undergoing relativistic transparency

Abstract

Control of the collective response of plasma particles to intense laser light is intrinsic to relativistic optics, the development of compact laser-driven particle and radiation sources, as well as investigations of some laboratory astrophysics phenomena. We recently demonstrated that a relativistic plasma aperture produced in an ultra-thin foil at the focus of intense laser radiation can induce diffraction, enabling polarization-based control of the collective motion of plasma electrons. Here we show that under these conditions the electron dynamics are mapped into the beam of protons accelerated via strong charge-separation-induced electrostatic fields. It is demonstrated experimentally and numerically via 3D particle-in-cell simulations that the degree of ellipticity of the laser polarization strongly influences the spatial-intensity distribution of the beam of multi-MeV protons. The influence on both sheath-accelerated and radiation pressure-accelerated protons is investigated. This approach opens up a potential new route to control laser-driven ion sources.

Polarization Dependence of Bulk Ion Acceleration from Ultrathin Foils Irradiated by High-Intensity Ultrashort Laser Pulses

“…The strong effect of the onset of pulse transmission in our conditions is also supported by transverse images of the proton beam on RCF; they are similar to those obtained in [38], where their relation with polarization-dependent relativistic transparency is discussed in detail. Overall, our results suggests that transparency effects are the main limiting factor for RPA at present.…”

Enhanced laser-energy coupling to dense plasmas driven by recirculating electron currents

“…This is despite the different laser pulse duration and other parameters explored, as detailed above. We note that for significantly thinner targets (sub-micron), which may become subject to hole-boring due to the laser radiation pressure or expand to the point that relativistic self-induced transparency occurs during the interaction, a different scaling with intensity is expected due to a transition from surface-dominated to volumetric interaction processes (see for example [27][28][29][30]).…”

Laser-driven acceleration of quasi-monoenergetic, near-collimated titanium ions via a transparency-enhanced acceleration scheme

“…With the recent development of high-power lasers, several new mechanisms have been identified. Two of the most promising advanced ion acceleration mechanisms are Radiation Pressure Acceleration (RPA) [27][28][29][30][31] and Relativistically Induced Transparency (RIT) [32][33][34][35][36][37][38]. RPA can potentially produce monoenergetic ion beams of higher energy than TNSA (E I max 2…”