Grating-lens metafiber with enhanced angular acceptance for broadband light coupling.

Efficient coupling of light into optical fibers is essential for a wide range of applications in telecommunications, sensing, imaging, and quantum photonics. Conventional fiber interfaces typically exhibit a limited angular acceptance interval, restricting their ability to efficiently collect and route light from off-axis sources. Here, we present a 3D-nanoprinted Metafiber that enables angle-selective coupling into a single-mode optical fiber while providing a broadband angular acceptance interval through a multiphase on-fiber grating lens. The device combines directional light coupling with suppression of undesired diffraction orders and is fabricated directly on spacer-enhanced fibers using high-resolution 3D nanoprinting. Optical characterization demonstrates efficient coupling over a substantially extended angular range while maintaining selective excitation of the fiber mode and strong zeroth-order suppression. These results establish a versatile Metafiber platform for directional light collection and spatial demultiplexing, offering new opportunities for fiber-based imaging, sensing, and integrated photonic systems.