An advanced focusing scheme, called a “flying focus,” uses a chromatic focusing system
combined with a broadband laser pulse with its colors arranged in time to propagate a high
intensity focus over a distance that can be much greater than its Rayleigh length while
decoupling the speed at which the peak intensity propagates from its group velocity. The
flying focus generates a short effective pulse duration with a small diameter focal spot that co-
or counter-propagates along the optical axis at any velocity. Experiments validating the …