Hierarchical Design and Optimization of Silicon Photonics

Abstract

Silicon photonics is a rapidly maturing platform for optical communication and sensing. As systems leveraging silicon photonics have grown in size and complexity, so too has the demand for high performance silicon photonics components. In order to meet these demands, we propose a hierarchical approach to design and optimization of silicon photonics components. Our approach applies simple physical analysis to choose an effective starting geometry for a two-step gradient-based shape optimization. This optimization employs carefully chosen geometrical constraints in order to consistently produce robust, high performance devices which satisfy practical fabrication constraints of deep UV lithography. In order to demonstrate the versatility of method, we optimize a 3 dB coupler which achieves better than 0.04 dB excess loss over the O-band, a four port 3-dB coupler which achieves better than 0.41 dB excess loss and near 50:50 splitting over the O-band, and a fabrication-tolerant waveguide crossing which achieves better than 0.075 dB insertion loss over the O-band even when subject to $\pm \text{10}$ % silicon thickness variations. These results pave the way for high efficiency silicon photonic component libraries.