Stability of Self-Configuring Large Multiport Interferometers

Realistic multiport interferometers (beamsplitter meshes) are sensitive to component imperfections, and this sensitivity increases with size. Self-configuration techniques can be employed correct these but not all equal. This paper highlights the importance of algorithmic stability in self-configuration. Na\"{\i}ve approaches based on sequentially setting matrix elements unstable perform poorly for large meshes, while power ratios well cases, even presence errors. Based insight, we propose a self-configuration scheme triangular meshes that requires only external detectors works without prior knowledge imperfections. extends rectangular mesh by adding single array along diagonal.