Spin and Wavelength Multiplexed Eight-Channel Surface Plasmon Metalensing

Abstract Recent demonstrations of metalensing have realized the selective coupling from free-space light into surface plasmon focusing beams, providing great possibilities for on-chip integration of division multiplexing and light routing. However, the surface plasmon wavefront control strategies of these metalenses can only work for a limited number of polarizations and wavelengths, resulting in four or less multiplexing channels. In order to break through the limitations of current SP metalens designs, we propose a holographic method with which we demonstrate, both theoretically and experimentally, that several surface plasmon metalenses can couple and steer the incident circular polarizations of four wavelengths and two spin directions to high-quality surface plasmon focusing beams, yielding a novel eight-channel multiplexing. The focusing directions for different free-space incidences can be flexibly designated, either different or the same. The proposed design strategy is straightforward and versatile, which may open up new opportunities in the realms of integrated photonics, on-chip spectroscopy, or plasmonic demultiplexers.