Fabrication-tolerant deep photonic networks with universal polarization handling capability

Photonic Integrated Circuits (PICs) have become widely used in application areas of optical computing, sensing and communications, where parallelization is crucial by dividing data processing pipelines into separate channels based on polarization. Although there are state-of-the-art devices achieving polarization-division multiplexing, polarization splitting, and polarization-independent power splitting, the increasing demand for achieving more complex optical tasks require scaling PICs which are limited by their manual design constraints and prior design knowledge. Here, a novel framework to design fabrication tolerant deep photonic networks of cascaded Mach-Zehnder Interferometers is demonstrated, achieving universal polarization handling tasks. Specifically, 50/50 and 5/95 fabrication-tolerant power splitters are implemented, achieving insertion loss below 0.5 dB and power deviations from the target optical transmission of 2% and 1.5%, respectively. Furthermore, the framework is extended to realize complex polarization management: a polarization splitter achieving an extinction ratio greater than 20 dB for both TE and TM polarizations with less than 0.5 dB insertion loss over a 120 nm bandwidth centered at 1550 nm; a polarization-independent 50/50 power splitter maintaining an insertion loss below 0.45 dB and a 0.5 dB target deviation, and a polarization-dependent arbitrary power splitter showing 0.4 dB deviation from the target -3 dB power for TE polarization and an extinction ratio exceeding 21 dB with 0.5 dB insertion loss for TM polarization, all within a 120 nm bandwidth between 1500-1600 μm wavelength.