Double slot high-k waveguide grating couplers for silicon photonics

Fully etched grating couplers are manufactured for double slot high-k waveguides. These couplers have a maximum efficiency of 22 %. This higher achieved efficiency despite the lack of a matching fluid compared to the case of single slots (18.5 % ) is due to the higher confinement of the optical power in the slot region for the double slot structures. Doubling the slot number reduces the effective refractive index from 2.7 to 2.2.