Compact All‐Fiber High‐Purity Vortex Laser via Controlled Linear Intracavity OAM Oscillation

ABSTRACT An orbital angular momentum (OAM) laser source has broad application potential in the fields of high‐capacity optical communications, super‐resolution imaging, and optical metrology. Although vortex lasers based on discrete optical elements have been reported, they are primarily generated in free space and constrained by their bulky size, which inevitably complicates integration with existing systems and restricts their applications. Here, we propose an all‐fiber vortex laser that enables intracavity vortex oscillations and the generation of OAM beams enabled by helically twisted fibers. The laser system consists of two classes of few‐mode fibers, namely, Er‐doped helically twisted fibers and spun fibers with a pitch of 2 mm, where the twisted active fiber maintains a gain coefficient of ∼1.48 dB/cm, ensuring sufficient gain for stable intracavity oscillations. Apart from the high compactness, the vortex laser system has demonstrated an excellent OAM beam purity up to 97% and a long‐term stability. Furthermore, the developed laser system was employed to detect the angular velocity of rotating object based on rotational Doppler effect, achieving an accurate and reliable measurement. This work addresses the limitations of existing OAM lasers through a compact, fully fiber‐integrated design, enabling their implementation in practical applications.