Sub-cycle time-varying orbital angular momentum beams

We explore the challenge of shaping the trajectory of light, weaving a dynamic spectrum of vortex beams through space and time. We successfully demonstrate a wave packet that spirals outwards in time (within a fixed transverse plane), and possesses an intrinsic self-torque. Moreover, our wave packets display sub-cycle temporal OAM variations on the order of a few femtoseconds. We show that this dynamic OAM remains conserved through adjustments in the beam’s radius—akin to the action of a mechanical wrench. Additionally, our work extends the concept to time-varying self-torque beams by introducing the first demonstration of angularly self-accelerating beams within a fixed transverse plane.