Momentum absorption and magnetic field generation by obliquely incident light

Abstract

The partial reflection of an electromagnetic (EM) wave from a medium leads to absorption of momentum in the direction perpendicular to the surface (the standard radiation pressure) and, for oblique incidence on a partially reflecting medium, also in the parallel direction. This latter component drives a transverse current and a slowly growing, quasi-static magnetic field in the evanescence "skin" layer. Through a simple model we illustrate how EM momentum is transfered to ions and estimate the value of the magnetic field which may be of the order of the driving EM wave field, i.e. up to several hundreds of megagauss for high intensity laser-solid interactions.

Key parameters for surface plasma wave excitation in the ultra-high intensity regime

“…This shows that the electrons dynamic is sensitive to the grating deformation. Other acceleration mechanisms along and across the surface have been suggested associated with the laser absorption: 39 indeed, we find that above a 0;T acceleration by SPW is not the main mechanism of electron acceleration, and the fast electron's angular distribution is much wider. This will be discussed in more detail in Sec.…”

Key parameters for surface plasma wave excitation in the ultra-high intensity regime

“…This shows that the electrons dynamic is sensitive to the grating deformation. Other acceleration mechanisms along and across the surface have been suggested associated to the laser absorption [39] : indeed we find that above a 0,T acceleration by SPW is not the main mechanism of electron acceleration, and the fast electrons angular distribution is much wider. This will be discussed in more detail in the next section, but we can anticipate that the analysis of the electron phase space confirms this hypothesis, since above a 0,T the electron velocity distribution does not show the characteristic behaviour of the acceleration by SPW, namely bunches with periodicity equal to the SPW wavelength, and directed along the surface [40].…”

On the control of electron heating for optimal laser radiation pressure ion acceleration

“…We further note that with oblique incidence (𝜃 0 > 0), the ion beam direction will be modified. This can happen due to partial absorption of the laser field, which will impart transverse (along the target surface) momentum to the ions (Macchi et al 2019) and also as the surface is modified to be nearly normal to the laser pulse causing the ion beam direction to be primarily along the laser propagation direction.…”