On the relation between periodically deflected and transverse mode-locked laser beams

Transverse mode-locked (TML) beams exhibit high-speed beam scanning, which motivates a comparison with established beam deflection technologies, such as galvanometer and voice coil scanners. This study explores the hypothesis that TML beams can be regarded as high-speed equivalents of such periodically deflected beams. By analytically modeling the spatiotemporal properties of TML beams as well as experimentally examining periodically deflected beams, both their intensity and phase dynamics were assessed. It is shown that TML beams yield a scanning motion which is shape-invariant upon propagation and have characteristic spatiotemporal phase dynamics. While TML-like scanning in intensity can be recreated by combining periodic translational and rotational deflection, beams deflected by mirrors still exhibit different phase dynamics. These findings imply that TML beams cannot simply be categorized as high-speed variants of periodically deflected beams. Nonetheless, TML beams remain applicable to high-speed laser beam scanning, although their phase dynamics have to be considered in phase-sensitive processes.