Nonlinear continuous orbital-angular-momentum modulation of linearly polarized Bessel beams

We numerically and experimentally demonstrate the nonlinear continuous modulation of orbital angular momentum (OAM) of a linearly polarized high -order Bessel beam in a biased photorefractive (PR) crystal. According to the simulation results, we identify three nonlinear dynamic regimes depending on the strength of the applied electric field, and we successfully stabilize the OAM via the modulation of a background illumination. As a result, we predict a parabolic trend for the maximal OAM modulation range in the stable regime. In addition, with the comparative analysis between vortex and differently truncated Bessel beams, we report the existence of exploitable plateaus, enabling a more extensive modulation range in the unstable regime. The experimental results are consistent with the simulations, confirming the practical realization of the flexible control of the OAM in both stationary and dynamic regimes. These results contribute to new reconfigurable components in OAM-based communications.