| CPC G02B 6/126 (2013.01) [G02B 6/1228 (2013.01); G02B 6/125 (2013.01); G02B 6/2773 (2013.01); G02B 2006/12035 (2013.01); G02B 2006/12061 (2013.01); G02B 2006/1215 (2013.01); G02B 6/2821 (2013.01)] | 20 Claims |

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1. A device, comprising:
a first lower waveguide and a second lower waveguide disposed on a first layer, the first lower waveguide and the second lower waveguide, in a first portion of the device, widening symmetrically as the first lower waveguide and the second lower waveguide extend from an input end of the device to an output end of the device, and, in a second portion of the device, at least the second lower waveguide widening further, asymmetrically, with respect to the first lower waveguide with an outer edge of the second lower waveguide that translates away from an inner edge of the second lower waveguide, wherein the inner edge of the second lower waveguide remains substantially unchanged from a position of the inner edge of the second lower waveguide in the first portion of the device; and
a bus waveguide disposed on a second layer, above the first layer, at least partially overlapping portions of the first lower waveguide and the second lower waveguide.
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