Quick Shot

An advanced focusing scheme has enabled a small-diameter laser focus to propagate nearly 100× its Rayleigh length. This technique removes the need for long-focal-length systems or guiding structures to maintain high intensities over long distances and decouples the velocity of the focal spot from the group velocity of the light. The photo shows a schematic of the chromatic focusing system coupled to a spectrally chirped laser pulse used to generate the “flying focus,” the name given to this advanced focusing scheme. Providing unprecedented spatiotemporal control over the laser focal volume allows the laser focus to co- or counter-propagate along its axis at any velocity. The article on flying focus is authored by Dustin Froula (shown in the image), David Turnbull, Andrew Davies, Terrance Kessler, Daniel Haberberger, Seung-Whan Bahk, Ildar Begishev, Robert Boni, Sara Bucht, Joe Katz, Jessica Shaw, and John Palastro.