Universality of comb structures in strong-field QED

We demonstrate a new mechanism for coherent comb generation in both radiation and matter domains, which is by using strong-field quantum electrodynamics processes. Specifically, we demonstrate this for nonlinear Compton scattering which has the potential to generate frequency combs extending towards the $\gamma$-ray spectral region as well as combs of ultra-relativistic electrons extending towards the MeV regime. Moreover, we show that coherent energy combs of positrons (or electrons) emerge in laser-induced pair creation processes such as the Breit-Wheeler process, proving the universality of the proposed mechanism.