Generating tunable multi-orbital angular momentum mode vortex beams by intracavity edge diffraction modulation

Abstract

In the past three decades, vortex beams (VBs) with orbital angular momentum (OAM) have attracted extensive attention in the fields of optical manipulation, image processing, optical communication, and optical measurement. Here, we demonstrate the generation of multi-OAM mode VBs using an intracavity diffraction edge modulation method by selectively “clipping” the high-order modes of the optical field through variable aperture diaphragms and variable slits. Multi-OAM mode VBs with 2, 3, 4, 6, 8, and 10 vortices are generated, and the phase singularities in vortices are verified through interference experiments. We propose the principle of intracavity mode superposition and obtain the corresponding intensity and phase profiles by simulation. The generated VBs can maintain stable OAM propagation within the range of 83 mm. This work breaks the traditional understanding of generating multi-OAM mode VBs and provides guidance for the design of special vortex laser devices.