Structuring orbital angular momentum beams by coherent laser array systems with tip-tilt optimization

Abstract

The generation and manipulation of high-power and mode switchable orbital angular momentum (OAM) beams have widespread applications such as free-space optical communication, nonlinear frequency conversion, and laser processing. To realize the power scaling and flexible mode switching, spatially structuring OAM beams with coherent laser arrays based on coherent beam combining technology provides a promising way. Up to now, the arrangement and piston phase control of the laser array system for tailoring OAM beams have been well explored. However, modulating only discrete piston phases of the array elements would limit the compensation of the dynamic aberrations and the precise generation of the desired structured light fields. In this paper, the coherent laser array system for tailoring OAM beams is improved by the introduction of the tip-tilt optimization. Based on the paraxial diffraction theory and coordinate transforming method, the theoretical model of the tip-tilt wavefront optimized coherent laser array that generates OAM beams is constructed. The results demonstrate that utilizing the tip-tilt optimization has the advantage in main ring power enhancement, and the introduction of tip-tilt control is required for compensating dynamic aberrations. Furthermore, the extended functions of the proposed laser array system in longitudinal and radial modulation of the combined OAM beams are discussed. This work could be useful for future implementation of customizing high-power and mode switchable structured light fields.