Enhancement of nonlinear pair production in a flying-focus pulse

Abstract

A photon can decay into an electron-positron pair in the presence of an intense laser pulse by a process known as nonlinear Breit-Wheeler pair production (NBWPP). For a sufficiently intense pulse, the probability of NBWPP for a high-energy gamma photon scales more favorably with the interaction time than with the field intensity. In contrast to typical stationary-focus Gaussian (SFG) laser pulses, a flying-focus (FF) pulse features a focal point that moves at a programmable velocity. Here, we show that a FF pulse counterpropagating with a high-energy photon beam while its focus copropagates with the beam at the speed of light enhances the NBWPP yield relative to an equal-energy SFG pulse. Numerical simulations show that a Joule-class tightly-focused FF pulse allows for an enhancement of the pair-production yield by 12\%, 29\% and 76\% for a photon of 10, 20 and 50 GeV energy, respectively. Thus, in this regime, FF pulses are more efficient at producing electron-positron pairs than conventional SFG pulses.