Simulation of Vector Mode Grating Coupler Interfaces for Integrated Optics

The use of grating couplers to couple light near vertically in and out of optical slab or film waveguides represents an attractive method to interface optical fiber to photonic ICs. Newly developed fiber technologies exploiting vector mode polarization and orbital angular momentum (OAM) are inherently threedimensional and interfaces for such beams require the solution of fully general 3D models, rather than the 2D models often used with ordinary grating couplers. In this work COMSOL Multiphysics was applied to the full 3D electromagnetic wave simulation of a novel forked grating coupler designed to interface with vortex modes of 1550 nm wavelength light. Full 3D models were solved for the radiating vector mode from a forked grating emitter structure driven from a nanophotonic waveguide. The results include interesting visualizations of vortex phasefronts, amplitude profiles, and polarization.