A Novel Working Scheme for Robust Optical Coupler Unit for Programable Unitary Matrices

Programmable optical unitary matrices (POUMs) in photonic integrated circuits (PICs) technology play a critical role modern information technology. With the expansion of their scale and integration density, POUMs have performance limited by fabrication errors tuning phase building blocks, i.e., tunable 2 × couplers. Here, we provide an in-depth theoretical analysis prior robust equivalent coupler demonstrate general requirement its passive beam splitters' split ratios, under which arbitrary transmission ratio can always be achieved. More importantly, analyze impact shifters' is caused voltage/current resolution electronic driving interface or thermal fluctuation. By analyzed result, propose novel working scheme for first time discovering unconventional configuration with large errors, against