Photonic integrated circuit system and method of fabrication

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.