Design and Fabrication of Low-Insertion-Loss and Low-Crosstalk Broadband Mach–Zehnder Silicon Photonic Switches

We present the design, fabrication, and measurement results of low-insertion-loss and low-crosstalk broadband 2 × 2 Mach-Zehnder switches for nanosecond-scale optical data routing applications. We propose a simulation framework to calculate the spectral characteristics of switches and use it to design two switches: one based on directional couplers, the other using two-section directional couplers for broader bandwidth. We show that driving the switch in a push-pull manner enables to reduce insertion loss and optical crosstalk at the expense of the optical bandwidth. We achieve a good correlation between simulations and devices fabricated in IBM´s 90-nm photonics-enabled CMOS process. We demonstrate a push-pull drive switch with insertion loss of ~1 dB and an optical crosstalk smaller than -23 dB over a 45-nm optical bandwidth in the O-band. We further achieve a transition time of ~4 ns with an average phase shifter consumption of 1 mW and a heater efficiency of ~25 mW/π.