Orbital angular momentum mode generation system based on photonic lantern

Abstract

We present an all-fiber-based method for generating orbital angular momentum (OAM) modes by using photonic lanterns in an adaptive-spatial mode control system. The device consists of a phase control part, a photonic lantern and a mode decomposition part. The use of photonic lanterns as adiabatic mode converters has been elaborated upon mathematically. To lock the desired OAM mode, the stochastic parallel gradient descent algorithm is used to control the phase modulators. The purities of the generated OAM modes with different topological charge are higher than 90% at 1550 nm, which has immediate utility for free-space propagation systems, and the superposition of different OAM modes at a specific ratio can be obtained to meet the requirements of mode multiplexing in optical fiber communication systems.