Modified mode transformer for detecting large-range OAM modes for the Laguerre-Gaussian beams

Abstract

Traditional signal multiplexing technologies have reached their limitations. Vortex beams exhibit a distinctive characteristic of orbital angular momentum (OAM), theoretically capable of providing infinite capacity, which allows for an increase in the information-carrying capacity of current optical networks, including both free-space optical (FSO) and fiber-based communication systems. In this paper, we propose an efficient approach to detect wide-range OAM modes using a mode transformer for the Laguerre-Gaussian (LG) beams. The mode transformer includes a phase mask (P1) that consists of three parts: the transformation term, the fan-out term, and the inverse term. And a phase corrector (P2). The fan-out mapper creates multiple copies of the transformed beams. After applying the phase mask, optical geometric transformations yield the optical matrix. Following phase correction, the light spots that form at the focal plane are identified by a CCD. We further extend the detection range by introducing an appropriate inverse phase to the P1 mask. Simulation tests have demonstrated outstanding detection performance, highlighting the potential of our proposed method to enhance the detection efficiency of multiplexed OAM beams.