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$.
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