| CPC G02B 6/34 (2013.01) [G02B 6/30 (2013.01)] | 19 Claims |

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1. A grating coupler comprising:
a substrate comprising a silicon wafer;
a first grating region having a first floor etched into the substrate,
wherein the first grating region comprises a first plurality of gratings having a first predetermined height measured relative to the first floor; and
a second grating region having a second floor etched into the substrate,
wherein the second grating region comprises a second plurality of gratings having a second predetermined height measured relative to the second floor,
wherein the first and second predetermined heights are not identical and a relative distance between the first floor and the second floor is not zero.
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