| CPC G02B 27/0172 (2013.01) [G02B 6/262 (2013.01); G02B 27/0081 (2013.01)] | 20 Claims |

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1. An electronic device comprising:
a waveguide;
a substrate on the waveguide;
a surface relief grating (SRG) in a first region of the substrate and having a first set of grooves;
a second set of grooves in a second region of the substrate, the grooves in the second set of grooves being narrower than the grooves in the first set of grooves;
a capping layer on the substrate and filling the first and second sets of grooves; and
an anti-reflective coating on the capping layer.
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