Relativistic interaction of long-wavelength ultrashort laser pulses with nanowires

TL;DR

This paper explores a new regime of relativistic laser-nanowire interaction using mid-infrared femtosecond pulses, achieving high energy absorption and plasma generation suitable for laboratory astrophysics and nuclear physics.

Contribution

It demonstrates efficient energy absorption and plasma creation using nanowires with long-wavelength lasers, advancing understanding of relativistic laser-matter interactions.

Findings

80% laser energy absorption into plasma

Generation of high-charge, keV-temperature plasma

Relativistic electrons achieved at low intensities

Abstract

We report on experimental results in a new regime of a relativistic light-matter interaction employing mid-infrared (3.9-micrometer wavelength) high-intensity femtosecond laser pulses. In the laser generated plasma, the electrons reach relativistic energies already at rather low intensities due to the fortunate lambda^2-scaling of the kinetic energy with the laser wavelength. The lower intensity suppresses optical field ionization and creation of the pre-plasma at the rising edge of the laser pulse efficiently, enabling an enhanced efficient vacuum heating of the plasma. The lower critical plasma density for long-wavelength radiation can be surmounted by using nanowires instead of flat targets. In our experiments about 80% of the incident laser energy has been absorbed resulting in a long living, keV-temperature, high-charge state plasma with a density of more than three orders of magnitude above the critical value. Our results pave the way to laser-driven experiments on laboratory astrophysics and nuclear physics at a high repetition rate.