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Design and optimization of photolithography friendly photonic components

Silicon photonics is a scalable, cost-effective technology for the production of photonic integrated circuits (PICs). The emergence of silicon photonics as a dominant technology for PICs is largely because it leverages decades of investment in design and fabrication technologies for electronic integrated circuits. However, the lithography requirements for photonic and electronic components are importantly different: geometries are generally curved; sidewall roughness is critically important; and, while the feature sizes are generally much larger, photonic device performance can be extraordinarily sensitive to the precise final geometry. For example, rounding of 90 degree corners in y-branches or multimode interferometers can have a dramatic impact on performance. The use of optical proximity correction (OPC) can greatly reduce these problems but does not eliminate them altogether. The designer is therefore faced with the problem of potentially optimizing a component using highly accurate numerical simulations that cannot be manufactured to the desired geometry, leading to a discrepancy between desired and actual performance. To solve this problem, we present a method for designing and optimizing photonic components that are lithography friendly so that the simulated geometry can be readily manufactured. As an example, we consider the case of waveguide Bragg gratings which are particularly challenging to manufacture by lithography.