Cherenkov radiation from a plasma*

The dispersion of electromagnetic waves in a plasma has traditionally precluded the emission of Cherenkov radiation into the far field: the phase velocity of the radiation exceeds the speed of light in vacuum and therefore the speed of a conventional driver. The flying focus—a moving focal point resulting from a chirped laser pulse focused by a chromatic lens—provides an intensity peak that can travel at superluminal velocities. Theory and simulations show that a plasma ponderomotively excited by a flying focus pulse can emit far-field Cherenkov radiation at THz frequencies.