Wavefront shaping of terahertz radiation using two-color flying-focus pulses

A two-color laser pulse can drive a current of photoionized electrons that emits broadband THz radiation. In conventional two-color configurations, the ionization front travels at a constant, superluminal velocity, generating THz radiation with conical wavefronts at a Cherenkov-like angle. These conical wavefronts can compromise collection and focusing of the radiation for subsequent applications. Here, we show that the dynamic intensity peak of a two-color flying-focus pulse can be used to control the shape of the THz wavefronts. Simulations demonstrate that non-uniform motion of the intensity peak—and the ionization front it produces—results in a time-dependent emission angle that determines the wavefront shape. A decelerating intensity peak, in particular, may enable the generation of THz radiation with parabolic phase fronts that are well suited for collection and focusing.