Cylindrical vector beam multiplexer/demultiplexer using off-axis polarization control

Cylindrical vector beam (CVB) multiplexing has emerged as a powerful technique to boost signal channels. Coupling and separating CVBs are two pivotal elements in CVB multiplexing communication. Although off-axis control technologies such as miniature Dammann vortex gratings have been investigated to couple and separate light beams, it is usually limited to light beams with homogeneous polarization due to its phase-only grating structure. For CVBs with inhomogeneous polarization, a gradient phase device is required to create a gradient phase difference between the left- and right-handed circularly polarized (LHCP/RHCP) components, so that the CVBs with off-axis incident angles can coaxially propagate and carry different phase structures. Despite considerable efforts of off-axis control technologies, the off-axis polarization control of CVBs still remains a challenge.

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