Phase Purity Measurement of Ultra-Broadband Orbital Angular Momentum Mode Excited by Meta-Facet Few-Mode Fiber

We design and fabricate metasurface on the facet of few-mode fiber (FMF). Ultra-broadband orbital angular momentum modes (OAM
₊₁
and OAM
_-1
) are excited in the fiber and the phase purity from 1480-1640 nm is measured through one interferogram image.