Description
The flying focus encompasses a variety of techniques for creating laser pulses with dynamic focal points. The peak intensity of a flying-focus pulse can move independently of the group velocity—along, against, or transverse to the propagation direction—while maintaining a near-constant profile over distances far exceeding a Rayleigh range. These features can enhance the wide range of laser-matter interactions that benefit from a tunable velocity or an extended interaction length. Here, we review the concepts underlying the flying focus and highlight recent advances in applications, such as laser wakefield acceleration, nonlinear Thomson scattering, free-electron lasing, direct laser acceleration, and fundamental tests of photon-photon scattering and radiation reaction.
