Collimated hot electron generation from sub-wavelength grating target irradiated by a femtosecond laser pulse of relativistic intensity

TL;DR

This study demonstrates that sub-wavelength grating targets irradiated by relativistic femtosecond laser pulses produce highly collimated hot electron beams with higher energies than planar targets, supported by experiments and simulations.

Contribution

It introduces the use of sub-wavelength grating targets to generate collimated hot electron beams with enhanced energy and coupling efficiency compared to planar targets.

Findings

Hot electrons are emitted in a collimated beam along the grating's specular direction.

Electron temperature is higher for grating targets than for planar mirrors.

Numerical simulations agree with experimental results and elucidate the acceleration mechanism.

Abstract

We investigate the production of hot electrons from the interaction of relativistically intense ($I> 10^{18} W/cm^{2}$) ultra-short (25 fs) laser pulses with sub-wavelength grating target. We measure the hot electron angular distribution and energy spectra for grating target and compare them with those from a planar mirror target. We observe that hot electrons are emitted in a collimated beam along the specular direction of the grating target. From the measured electron energy spectra we see electron temperature for grating is higher than the mirror, suggesting a higher electron yield and hence a stronger coupling with the laser. We performed numerical simulations which are in good agreement with experimental results, offer insights into the acceleration mechanism by resulting electric and magnetic fields. Such collimated fast electron beams have a wide range of applications in applied and fundamental science.