Field-driven attosecond deflection of electron beams at the position of planar foils

Abstract

While the coupling of free-electron beams and light has enabled the control of quantum states in electrons and the generation of ultrashort electron pulses, it can induce artifacts when probing a laser-driven sample with an electron beam. Here, we theoretically study optical-field-driven beam deflection that inevitably occurs at the location of a laser-excited sample. Treating electrons in a beam as classical point particles and focusing on thin planar samples, we conduct a systematic study of the instantaneous deflection amplitudes with respect to light polarization, material type, thickness, and interaction geometry. For s-polarized excitation fields, the deflection amplitude is strictly proportional to the excitation-field amplitude in a foil, making beam deflection unavoidable. Conversely, for p-polarized fields, a nontrivial relationship emerges between the deflection amplitude and the field amplitude due to the interplay of electric and magnetic fields coupled with the electron-light velocity mismatch. Crucially, we demonstrate that the deflection can be minimized even under high field strengths by selecting an optimal configuration for a given foil material and thickness. These findings provide key guidelines for designing future time-resolved imaging experiments using ultrashort electron beams.