Generalized Mach Zehnder Interferometers Integrated on Si₃N₄ Waveguide Platform

We demonstrate 3 × 3 and 4 × 4 Generalized Mach Zehnder Interferometers (GMZI) integrated on the Si ₃ N ₄ waveguide platform and present their experimental performance as switching and variable power splitting modules. The GMZI structures have been theoretically modelled by means of a transfer matrix model, evaluating also the GMZI spectral response in the case of fabrication errors that may lead to variations in GMZI arm lengths, MMI phase shifts and MMI splitting ratios. Both 3 × 3 and 4 × 4 GMZI structures were fabricated as integrated Si ₃ N ₄ -based circuits and were experimentally characterized with the experimental results being in close agreement with the theoretical predictions. They both reveal a resonant spectral behavior with an FSR of 1.9 nm and low average insertion losses per port that were measured to be 1 ± 0.2 and 2.4 ± 0.4 dB. The two GMZI structures were utilized as 1:3 and 1:4 switching elements, respectively, with average crosstalk levels being always greater than 10 dB for all possible input-output port combinations. Finally, their credentials to serve within linear optical circuit implementations were evaluated through their experimental characterization in variable power splitting applications, showing that the power level at a single output port can take any value between 0 and 100% of the input signal.