Broadband Structured Light Multiplexing With Dielectric Meta-Optics

Structured light beams (SLBs), mainly including vortex beams (VBs) and cylindrical vector beams (CVBs), have received significant attention in optical communications due to orthogonal orbital angular momentum (OAM) or vector modes. However, the mode conversion between OAM and vector modes and the working bandwidth are always challenges restricting the practical applications. Here, we demonstrate broadband SLB multiplexing in optical communication with dielectric Pancharatnam-Berry phase-based metasurfaces (PBMs). By virtue of the dispersion-free characteristic and spin-orbital interaction, the designed metasurfaces have a broad working wavelength ranging from C- to L-bands and can flexibly convert VBs and CVBs. With these properties, SLBs are successfully multiplexed with conventional physical dimensions (including wavelengths and polarization states) to construct complex multiplexing formats. In a back-to-back free-space transmission experiment, 50 Gbit/s quadrature-phase shift-keying (QPSK) signals are used for multiplexing with four OAM modes, seven wavelengths, and two polarization states. When the transmission rate reaches 2.73 Tbit/s, the bit-error rate (BER) is below 10
^-6
at an optical signal-to-noise ratio (OSNR) of 17 dB. By changing the polarization states of the incident light, CVB multiplexing is realized, and the BER is below 10
^-6
at an OSNR of 19 dB.

Owing to the silica substrate, PBM is capable of photonic integration, and it is anticipated that this PBM may provide a new avenue for high-order multiplexing and all-optical signal processing of SLBs.