Fiber Integrated Orbital Angular Momentum Sorter

Orbital angular momentum (OAM) beams, characterized by their helical wavefront and azimuthal phase dependence, have emerged as powerful carriers for high‐dimensional optical information, fueling advances in communications, imaging, and quantum technologies. A key challenge, however, remains the efficient and robust sorting of OAM modes—especially within compact, alignment‐tolerant systems that integrate seamlessly with fiber platforms. Here, we introduce a fiber‐endface‐integrated OAM sorter, fabricated monolithically on a single‐core few‐mode fiber via two‐photon lithography. The device incorporates a half‐Fresnel zone plate (HFZP) directly patterned onto the fiber facet, enabling on‐chip spatial mode discrimination without free‐space optics or critical alignment. This integrated design yields a highly compact and stable configuration, achieving distinct far‐field separation of OAM modes with inter‐modal spacing up to 52 µm on a CCD. Experimental results demonstrate simultaneous detection of multiple OAM modes spanning topological charges from −4 to +4. By obviating bulky optics and alignment‐sensitive components, our approach offers a scalable pathway toward fiber‐compatible OAM processing systems. This work marks a notable advancement in miniaturized OAM multiplexing architectures, with promising applications in high‐capacity optical communications and integrated quantum photonics.