| CPC G02B 6/12019 (2013.01) [G02B 6/132 (2013.01); G02B 6/136 (2013.01); G02B 2006/12061 (2013.01)] | 18 Claims |

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1. A method of fabricating a photonic integrated circuit (PIC) on a substrate, comprising:
lithographically defining a transition between a first photonic circuit block and a first connecting waveguide having a first width using a first lithographic patterning technique, the photonic integrated circuit comprising:
a transition waveguide having a second width, configured for optically coupling to a photonic element in the first photonic circuit block; and
a transition feature extending between the transition waveguide and the first connecting waveguide, tapering from the first width to the second width;
wherein defining the transition feature and the transition waveguide comprises providing a tapered masked feature over the first connecting waveguide and the first photonic circuit block configured to define the transition feature and the transition waveguide; and
wherein the tapered masked feature has a maximum width greater than the first width, and extends past the first width in both directions.
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