High‐Purity Circularly Polarized Collimated Beam Generation via Metasurface‐Enabled Fiber Device

ABSTRACT Generation of a circularly polarized collimated beam is crucial in various photonic systems, such as bio‐imaging systems, on‐chip integration systems, and quantum sensing platforms. Yet, conventional approaches relying on cascaded bulk optics (e.g., collimating lenses, waveplates, and polarizers) significantly increase system footprint and alignment complexity. Here, we present a compact metasurface‐enabled fiber device that directly generates high‐purity, low‐divergence circularly polarized beams. The device employs a single‐layer transmissive metasurface, with a glass‐tube‐based assembly method for connecting the metasurface to the fiber. Experimental characterization demonstrates a half‐divergence angle below 0.02, circular polarization purity exceeding 0.993 across the entire beam, and a transmission efficiency of 68% for the target polarization state. This work provides a compact, fiber‐compatible solution for simultaneous beam collimation and polarization control, with immediate applications in atomic magnetometers, quantum sensing, and other space‐constrained photonic systems.