Scalable and Robust Photonic Integrated Unitary Converter Based on Multiplane Light Conversion

An optical unitary converter (OUC) that can convert a set of $N$ mutually orthogonal modes into another arbitrary is expected to be key device in diverse applications, including communication, deep learning, and quantum computing. While various types OUC have been demonstrated on photonic integration platforms, the sensitivity against slight deviation waveguide dimensions has crucial issue scaling $N$. Here, we demonstrate an based concept multiplane light conversion (MPLC) shows outstanding robustness deviations. Moreover, it becomes more insensitive fabrication errors as increase $N$, which clear contrast conventional architecture, composed $2\ifmmode\times\else\texttimes\fi{}2$ Mach-Zehnder interferometers. The physical origin behind this unique scalability studied by considering generalized configuration. As result, reveal number coupled each stage plays essential role determining entire OUC. maximal attained when all-to-all-coupled interferometers are employed, naturally implemented MPLC-based