Orbital angular momentum control of strong-field physics in gas phase

Abstract Photoionization plays a pivotal role in several physical, chemical, and biological processes. When induced in an atom or molecule by an intense laser pulse, the electron dynamics in the laser field lead to new phenomena that form the basis of attosecond science. Ultra-intense laser pulses can also accelerate electrons to relativistic energies through ponderomotive force or laser-plasma interaction. Most light-matter interactions involve Gaussian beams, where control over ionization and electron dynamics is typically governed by polarization and carrier-envelope phase of the light pulse. In this article, we reveal that Orbital Angular Momentum (OAM) carrying beams provide a new dimension to control strong-field ionization of atoms and molecules. The ionization process is influenced by the sign and value of the OAM and can be manipulated by displacing the phase singularity in the beam. We show that the field gradients inherent in the higher-order multipole expansion of the tunneling process cause ionization to depend on OAM. Simulations indicate that, in contrast to Gaussian beams, the ponderomotive energy and the average force can be controlled by OAM and by displacing the phase singularity in the optical vortex. Our findings have broader implications in the realms of plasma physics, attosecond science, atomic and molecular spectroscopy, and super-resolution microscopy.