Abstract
Employing couplers to convert guided waves into free-space modes and flexibly control their wavefront is one of the key technologies in chip-integrated displays and communications. Traditional couplers are mainly composed of gratings, which have limitations in footprint, bandwidth, as well as controllability. Though the resonant/geo-metric metasurface newly emerges as a promising interface for bridging guided waves with free-space ones, it either relies on complex optimizations of multiple parameters, or is subject to the locked phase response of op-posite spins, both of which hinder the functional diversity and practical multiplexing capability. Here, we propose and experimentally demonstrate an alternative with a spin-decoupled meta-coupler, simultaneously integrating triple functions of guided wave radiation, polarization demultiplexing, and dual-channel wavefront manipulation into a single device. By endowing polarization-dependent functionalities into a pure geometric metasurface, the out-coupled left-handed and right-handed circular polarization guided waves intelligently identify the prede-signed phase modulation and reconstruct desired wavefronts, like bifocal focusing and holography multiplexing, with a polarization extinction ratio over 13.4 dB in experiments. We envision that the robust, broadband, and multifunctional meta-coupler could pave a way for the development of versatile multiplexed waveguide-based devices.(c) 2023 Chinese Laser Press