| CPC G02B 6/34 (2013.01) [G02B 6/2726 (2013.01)] | 20 Claims |

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1. An optical grating coupler, comprising:
a primary layer formed of a material having a first refractive index, the primary layer having a top surface;
a first plurality of scattering elements formed within the primary layer, the first plurality of scattering elements having a second refractive index that is different than the first refractive index, wherein each of the first plurality of scattering elements has a cross-shaped cross-section oriented parallel to the top surface of the primary layer;
a secondary layer formed over the primary layer, the secondary layer formed of a material having a third refractive index, the secondary layer having a top surface; and
a second plurality of scattering elements formed within the secondary layer, the second plurality of scattering elements having a fourth refractive index that is different than the third refractive index, wherein the fourth refractive index is different than the second refractive index, wherein each of the second plurality of scattering elements has a cross-shaped cross-section oriented parallel to the top surface of the secondary layer, wherein at least some of the second plurality of scattering elements at least partially overlap corresponding ones of the first plurality of scattering elements.
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