Generating Orbital Angular Momentum (OAM) Beam with Continuously Tunable Operating Frequency/Topological Charge without Phase-shifter

In this paper, a method for generating Orbital Angular Momentum (OAM) based on fixed delay lines is proposed. By derivating the relationship between the signal frequency applied to the delay line and the topological charge of OAM, the topological charge can be controlled by controlling the frequency. The proposed method not only has the advantages of simple structure and low cost, but also can generate OAM with continuously adjustable topological charge by controlling the frequency, which has the functions of topological charge reconstruction and dynamic adjustment.