Speaker
Description
Accurate representation of electromagnetic wave packets in particle-in-cell simulations is crucial for ensuring that the outcomes closely align with experimental results. Conventional methods for laser injection rely on the paraxial and envelope approximations, effective for beams that are both long and wide with respect to the laser's wavelength. However, new laser systems are advancing towards shorter pulse durations (down to single-cycle) and more focused spot sizes (near or at the diffraction limit), enabling higher intensities. Under these new conditions, the assumptions underlying the said approximations break.
Here, we propose an exact injection method tailored for arbitrarily shaped lasers in particle-in-cell codes that exactly satisfies Maxwell’s equations without any approximation. It allows injecting pulses based on the outputs of standard experimental diagnostics (e.g., spectrum and spectral phase measurements), and is ideal to inject structured light pulses with spatiotemporal couplings.
We employ this novel technique to show that the interaction of electron bunches with intense structured lasers in nonlinear Thomson scattering can be used to control the spatiotemporal structure of the resulting radiation. As an example, we use this approach to convert orbital angular momentum (OAM) into transverse optical angular momentum (TOAM), thereby creating spatiotemporal optical vortices (STOV) in nonlinear Thomson scattering.
