Fig. 1: Schematic of microbunching in a laser pulse.

a Collision of e⁻/e⁺ bunch (blue and red dots) with a plane wave of wavelength λ₀ (red lines) to produce harmonics of radiation starting from λ₁ (green curved lines). b Microbunching due to the interaction of the bunch with its self-generated radiation, at the laser pulse peak. Here λ₁ controls the microbunch separation and provides an upper limit of the width FWHM_mb.