Azimuthal backflow in light carrying orbital angular momentum

M. V. Berry's work [J. Phys. A 43, 415302 (2010)] highlighted the correspondence between backflow in quantum mechanics and superoscillations in waves. Superoscillations refer to situations where the local oscillation of a superposition is faster than its fastest Fourier component. This concept has been used to experimentally demonstrate backflow in transverse linear momentum for optical waves. In the present work, we examine the interference of classical light carrying only negative orbital angular momenta, and in the dark fringes of such an interference, we observe positive local orbital angular momentum. This finding has implications for the studies of light-matter interaction and represents a step towards observing quantum backflow in two dimensions. (c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement