Mach–Zehnder silicon-photonic switch with low random phase errors

A Mach–Zehnder silicon photonic switch with low random phase errors is proposed and demonstrated for the first time, to the best of our knowledge, by incorporating judiciously widened and shortened phase shifter waveguides. With a 180 nm complementary metal–oxide–semiconductor (CMOS) foundry process, more than one hundred 2 × 2 thermo-optic Mach–Zehnder switches (MZSs) with varied phase shifter widths have been designed, fabricated, and characterized on 14 silicon chips. The mean and standard deviation of the random phase errors of the MZSs with phase shifters widened to 2 µm are less than a third of those of the conventional design with 0.45-µm-wide single-mode phase shifters. This validates the improved fabrication tolerance and results in considerable reduction of the power consumption for the phase error compensation. Such elegant methodology paves the way to further scaling up N × N silicon thermo-optic switches and can be generalized for other phase-sensitive integrated photonic devices as well.