FDTD-Based Simulation of Submicron Laser-Plasma Interaction

Laser-plasma interactions play a crucial role in high-energy particle generation and acceleration, where target geometry and pre-pulse shaping significantly influence energy transfer. In our previous work with 15-micron spherical targets, we observed a notable enhancement in electron temperature—from 50 keV to 200 keV—due to the presence of a pre-pulse. Electrons were accelerated to MeV energies, a phenomenon attributed to pre-pulse-driven pre-plasma formation and plasmon excitation. Remarkably, when we scaled down to targets comparable in size to the laser wavelength, we observed a similar enhancement, demonstrating that the pre-pulse effect remains significant even for sub-wavelength targets.

However, standard radiation hydrodynamics models become inadequate in this regime, as ray-tracing methods lose accuracy and conventional absorption models break down. To address this limitation, we have developed a specialized code that couples a Finite Difference Time Domain (FDTD) electromagnetic solver with plasma evolution equations. This code enables accurate modeling of early-stage plasma dynamics in sub-wavelength targets, offering new insights into laser-matter interactions and informing the development of more reliable predictive models.