Toward Topology-Optimized Foundry PDKs: A Seeded Design Framework for Multimode Interferometers

Abstract

We present an end-to-end design methodology for multimode interferometer (MMI)-based photonic devices that combines parameter optimization (PO) on analytical models with seeded topology optimization (TO) to maximize performance while preserving foundry design-rule compliance. A PO seed device is further refined via seeded TO, accessing a larger design space than analytical or parameterized methods alone can reach. We validate this pipeline on a 1x2 splitter, a TE modal multiplexer, and a polarization splitter, with the first two fabricated on a commercial foundry process and measured. Seeded TO reduces the measured insertion loss of the 1x2 splitter from 0.20 to 0.14 dB and improves the back-to-back TE00 transmission of the modal multiplexer from -2.38 to -0.99 dB over 1274-1326 nm. Applying this pipeline to a commercial foundry process design kit (PDK)-provided 1x2 and 2x2 splitters improve measured transmission and bring the measured 2x2 splitting ratio from 0.520 to 0.499, along with improved simulated fabrication robustness, offering a practical, foundry-validated route toward incorporating TO-designed components into commercial PDKs.

arXiv comment19 pages, 5 figures