Meta-facet fiber for twisting ultra-broadband light with high phase purity

From metamaterial to metasurface and metadevice, the artificial structure with sub-wavelength scale on diverse platforms offers the ability to shape light in a custom way. The optical fiber is a robust and flexible media that has seen wide applications in optical communications, optical sensing, microscopy, and endoscope imaging. Here, we consider metasurface on a large-core fiber platform for twisting light. Using the designed and fabricated meta-facet fiber, we demonstrate (i) the excitation of both linearly polarized and circularly polarized twisted light (OAM+1, OAM−1) from either meta-facet side or planar-facet side, (ii) phase-front reconstruction of twisted light simply from a tilt interferogram using the Fourier-transform method, and (iii) ultra-broadband response from 1480 to 1640 nm with high phase purity above 93% for twisting light. The demonstrations on meta-facet fiber for twisting ultra-broadband light with high phase purity may open up perspectives to more emerging applications in information, biology, and medical science.