Chip-integrated metasurface for versatile and multi-wavelength control of light couplings with independent phase and arbitrary polarization

Abstract

While metasurfaces are now widely considered in free-space optics, their potential for coupling and tailoring guided waves is not fully explored. Here we transfer the Jones matrix method to target versatile on-chip coupling using metasurface-patterned photonic waveguides around the telecommunication wavelength of 1.55 μm, which can accommodate both propagation and Pancharatnam-Berry phase metasurfaces for guided waves. One can either encode two arbitrary and independent phase profiles to any pair of orthogonal polarizations or deploy complete control over both the phase and polarization of coupled modes. A set of design scenarios synergizing silicon nanoantennas and low-loss silicon-nitride waveguides are proposed, including directional couplers with mode-selectivity and polarization splitters with directionality ranging from 10 to 20 dB. Furthermore, our optimization method can be further extended to cover multiple working wavelengths. Exemplary on-chip color routers are also numerically demonstrated. This chip-integrated metasurface platform further translates the concept of a metasurface into photonic integrated circuits, serving as a positive paradigm for versatile and complete control over waveguide optical signals and motivating chip-scale applications such as polarization/wavelength demultiplexers, optical switches, and multifunctional mode converters.