Coupling light into photonic integrated circuits using non-periodic surfaces

We report a critical assessment of the use of non-uniform gratings for enhancing light coupling to photonic integrated circuits (PICs). Grating couplers, performing as a very attractive vertical coupling scheme for the silicon waveguide, have been widely demonstrated. It is shown that the coupling efficiency of grating couplers can be enhanced by using an Inverse Design (ID) methodology that can deal simultaneously with many physical and geometrical parameters. Moreover, this method paves the way for designing non-uniform gratings in an efficient way, which not only match the coupling efficiency of conventional periodic corrugated waveguides but also allow to devise more sophisticated components such as wavelength or polarization splitters.