Metasurface-Based Fiber-to-Chip Multiplexing Coupler

摘要

Here, a metasurface-based fiber-to-chip multiplexing coupler is presentedthat can realize flexible mode conversion and multiplexing coupling betweenfew-mode fibers and on-chip single-mode waveguides. The proposedapproach makes use of the symmetrical characteristics of fiber eigenmodesand high freedom of light phase manipulation to obtain the functional phasedistribution of metasurfaces. The use of cylindrical nanopillar as metasurfacenanostructures ensures its polarization independent optical response. Severalfiber-to-chip multiplexing couplers are demonstrated by using the angularspectrum methods and the finite-difference time-domain (FDTD) simulations.It is found that the two or three modes can be flexibly demultiplexedand then be coupled into the corresponding on-chip waveguides with lowcrosstalk. Further, two possible fabrication schemes for multiplexing couplersare proposed and then the related fabrication tolerances and misalignmenteffects are evaluated and discussed. Compared with traditional on-chip couplers,metasurface-based couplers have advantages of ultracompact footprintand low crosstalk. Such study explores the application of metasurfaces inmultiplexing coupling between few-mode fiber and on-chip single-modewaveguides, which is expected to break through the bottleneck of currentmode-division multiplexing technologies in optical interconnection and meetthe ever-increasing demand for large data throughput of the photonic integratedchips.