The generation of axial multiplane optical angular momentum based on liquid crystal device

Abstract

The demand for high capacity and integration in modern optical communication technology is becoming prominent. Orbital angular momentum (OAM) plays an important role in optical communication. However, there are still challenges to further expand the flexibility and capacity of optical communication in the axial direction. Here, we propose a single-layer liquid crystal device (LCD) to realize the generation of optical vortex (OV) array with arbitrary topological charge in axial multiplane, which can be applied in optical communications based on highly integrated device. The phase of the target OV array is weighted and superimposed to obtain the phase distribution of LCD. In order to obtain an OV array with uniform intensity, it is necessary to determine the optimal weight factor for each OV based on the introduced particle swarm optimization (PSO) algorithm. In the experiment, a LCD with an effective aperture of 2 mm was processed. A CCD captures the OV array image, including two OV arrays at 200*λ (156μm) in front of and behind the focal point respectively. Then, the beam passes through the 4f system of the spatial light modulator with the phase distribution of the Damman vortex grating on the spectrum plane, and the topological charge of the two OV arrays can be detected by the CCD. Our results provide an approach that based on a single liquid crystal plate, OV arrays in multiple propagation planes are realized, in which the number of propagation planes and the position of each propagation plane relative to the back focal plane can be adjusted arbitrarily, and the number, order, and position of OVs in each propagation plane can also be adjusted arbitrarily to meet the application requirements in the field of short-distance optical communication.