Non-mechanical axial focus tuning by coherent beam combining technique

Abstract

High-speed variable-focus optics brings new opportunity to the applications of fiber laser in the fields of advanced laser processing, laser three-dimensional (3D) printing, imaging and so on. As an emerging field, variable-z-focus optical elements have been developed rapidly. There are many approaches to achieve high-speed variable focus such as ferroelectric liquid crystal lens, acoustically driven fluid lenses and enhanced adaptive optical technologies. In this paper, a method of non-mechanical axial focus tuning by coherent beam combining (CBC) technique is investigated. The method does not depend on any made-to-order element to achieve the high-speed variable focus. We provide detailed design processes and theoretical basis of how to achieve focus tuning by CBC technique. Then, the influencing factors of the tunable range of focus are analyzed. We also propose a tilt modulation assisted method in this paper to extend the tuning range furtherly. Finally, a visual demonstration is carried out by spatial light modulators to verify the method and achieving 10 cm tuning range of focus point.