PIC simulations characterizing the THz radiation response of a copper target excited by an ultra-short laser pulse

                The interaction of an intense, ultrashort-pulse laser with a solid target leads to dramatic modification of its surface and subsequent emission of electromagnetic (EM) radiation. This radiation may be an interesting probe of the laser-target interaction or useful in its own right. We have used 2D LSP [1] particle-in-cell (PIC) simulations to characterize the THz range radiation response of copper targets illuminated by single high intensity ultra-short laser pulses with intensities up to 10¹⁸ W/cm². Our simulations treat the material permittivity and reflectivity using a realistic collision model [2] based on the binary collision algorithm. This permits a realistic treatment of the target’s dynamically changing electromagnetic response and thermal evolution beginning from a room temperature state, which then establishes the initial conditions for the subsequent current evolution and EM emission. Accordingly, we describe efforts to model the evolution over several picoseconds using staged simulations covering first the laser-target interaction and then the subsequent evolution of the target. We measure the resulting EM emission in the target near-field looking at both the spectrum and angular distribution.

[1]      Welch, D. & Rose, D., Comp. Phys. Comm. 164, 183-188 (2004)

[2]      A.M. Russell and D.W. Schumacher, Physics of Plasmas 24, 080702 (2017).