Broadband bifunctional manipulation of a fiber-emitted sub-wavelength structure light beam based on a fiber-integrated metasurface

Structured light beams have significant application value in fields like optical communication, microscopic imaging, and biomedicine due to their unique spatial field distribution characteristics. However, traditional structured beam generation systems based on discrete optical components have inherent drawbacks such as strict alignment requirements and poor tunability, which severely limit their practical applications. This paper proposes a new method for broadband bifunctional generation of structured beams based on fiber-integrated metasurfaces: by integrating spin-multiplexing bifunctional phase metasurfaces with the end faces of optical fibers, broadband sub-wavelength Bessel beams and focused vortex beams were, respectively, generated on demand in an all-fiber configuration when different circularly polarized light was input. The experimental measurements showed that the transmission characteristics of the generated beams were highly consistent with the numerical simulation results. Our scheme fully exploits the flexible waveguide (bendable) advantage of fibers, breaking through the constraint of poor optical path tunability in traditional “hard connection” systems due to strict alignment requirements. Since the implemented device simultaneously possesses broadband operation, sub-wavelength-scale field control, and spin-multiplexing characteristics, this study provides a new paradigm for multidimensional and multifunctional dynamic light field manipulation, and it holds significant application potential in fields such as fiber-optic imaging and fiber sensing.