| CPC G02B 6/136 (2013.01) [G02B 6/1223 (2013.01); G02B 6/132 (2013.01); G02B 2006/12038 (2013.01); G02B 2006/12111 (2013.01)] | 25 Claims |

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1. An apparatus comprising:
a substrate, the substrate including a channel that extends into a first surface of the substrate to a second surface of the substrate, the second surface recessed relative to the first surface;
a buffer material on the second surface of the substrate, the buffer material having a first index of refraction, the buffer material including a first portion and a second portion spaced apart from the first portion, both the first and second portions of the buffer material on the second surface of the substrate with the second surface extending continuously between the first and second portions;
a first waveguide on the buffer material, the first waveguide having a second index of refraction that is higher than the first index of refraction; and
a second waveguide on the second portion of the buffer material, the second waveguide spaced apart from the first waveguide, the first waveguide having a first side surface facing toward a second side surface of the second waveguide.
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