Strong-field electrodynamics in Flying Focus pulses

2026-07-22

"In this action, we propose a theoretical investigation of charged particle behavior in external laser fields using the recently-described “flying focus"" (FF) regime, a laser field setup which allows precise control of the position and velocity of its focus. This novel regime makes it possible to adjust the laser focus so that it co-propagates with the particle, including the situation when the particle is moving against the laser phase fronts. The resulting long laser-particle interaction time enabled by FF pulses is expected to significantly enhance radiation reaction, methods of particle beam control, and cumulative magnetic moment effects along the particle trajectories. In the classical relativistic framework, this will give us the possibility to test the equations of motion, which include radiation-reaction terms and Stern-Gerlach force in the case of particles with spin. In the quantum framework, we will first investigate analytically the probability of single photon emission by a high energy electron in a flying focus beam, and then study numerically the cascade emission of several photons (quantum radiation reaction). Finally, we will implement flying focus fields and the calculated probabilities of the quantum emission processes into the Particle-In-Cell code SMILEI. With this code, we will perform simulations of experimental setups exploiting flying focus fields in laser-particle interactions. Thus we will identify viable experiments that could lead for the first time to unambiguous radiation reaction detection, allow for methods of particle beam control, and enable us to probe quantum electrodynamics in the strong field regime."

Czech Republic

2025-10-15