In OptoDesigner, the concept of a Mask Cross-Section (MCS) was introduced to abstract away the physical implementation of a waveguide from the design intent. The user draws what they would like to get on the chip, and the MCS concept makes sure that all the correct mask layers are generated, all following the exact shapes that the user specified. This feature highlight shows exactly how that is to be implemented by a PDK developer and shows the full range of capabilities.
A simple example is show below, where the design intent is a simple 90-degree bend, but the mask layers required for that are trenches around the waveguide – essentially, a local inverse of the design intent.