Emission direction of fast electrons in laser-solid interactions at intensities from the nonrelativistic to the relativistic

Abstract

The emission direction of outward-ejecting fast electrons generated in laser-solid interactions by 30 fs laser pulses is measured for laser intensities varying from the nonrelativistic to the relativistic. For an s-polarized incident laser beam at nonrelativistic intensities, the ejected electrons are close to the polarization direction of the laser beam. With the increase of the laser intensity, the ejected electrons are still mainly within the polarization plane, but turn away from the laser polarization direction towards the opposite direction of the incident laser beam. At relativistic intensities, electrons eject towards the direction of the reflected laser beam. The increasing ponderomotive force acceleration with the laser intensities might be responsible for the observed changes.