Design and Fabrication of Low-Insertion-Loss and Low-Crosstalk Broadband $2\times 2$ Mach–Zehnder Silicon Photonic Switches

We present the design, fabrication, and measurement results of low-insertion-loss and low-crosstalk broadband $2\times 2$ 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 $\sim$ 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 $\sim$ 4 ns with an average phase shifter consumption of 1 mW and a heater efficiency of $\sim$ 25 mW $/\pi$ .