Crosstalk-assisted thermo-optic switching on a silicon photonics platform

Key performance metrics for thermo-optic switches often exhibit inverse relationships. This study examines a symmetric thermo-optic Mach–Zehnder interferometer (TO-MZI) switch across a 3.5–41.5 µm interferometric waveguide gap range, and an asymmetric TO-MZI switch across a 7.5–22.5 µm interferometric waveguide gap range, evaluating the correlated impact of footprint, thermal crosstalk, switching time, and power consumption. Simulations and experimental investigations lead us to summarize device performance via a defined figure of merit (FoM). We demonstrate that there exists an optimized physical gap between interferometric waveguide arms which results in improved overall performance. Specifically, gap optimization provides a minimum footprint below which switching power increases significantly. We also show the impact of this optimization on switching time, which is reduced as the gap decreases. These findings highlight the trade-offs and benefits of gap tuning in the TO-MZI design.