Modulation of orbital angular momentum of vortex beam based on ordered pinhole screens

Optical vortex phase beams have unique amplitudes and phase distributions, rendering them sensitive to the position and symmetry of modulating structures. This sensitivity can facilitate their applicability to optical communications. We propose a method for modulating the topological charge of input vortex beams using a pinhole screen. By changing the pinhole arrangement to match the phase of the vortex beam and considering the Fresnel diffraction theory, the transmission light field is calculated numerically. In addition, the intensity map of the adjustable topological charges is measured near the origin, with the experimental results suitably agreeing with the theoretical simulation results. The diffraction field modulated by spiral pinholes has various orbital angular momentum modes, including the increase and decrease of orbital angular momentum, especially when the incident vortex beam is more complex. The proposed method opens new possibilities for the use of vortex beams in advanced optical applications with improved capabilities and functionalities.