Compact 2 × 2 silicon thermo-optic switch with <i>P</i> _π of ∼ 1.4 mW and extinction ratio &gt; 28 dB over C-band

We have designed and experimentally demonstrated a compact 2 × 2 silicon thermo-optic Mach-Zehnder switch with a P π of ∼ 1.4 mW and an extinction ratio of &gt; 28 dB over C-band. We use spiral configurations for both the silicon waveguide and the metal heater in the phase shifters to improve thermal efficiency. The densely packed silicon waveguides are connected by hybrid Euler bends. The adjacent straight waveguides have different widths of 400 nm and 550 nm to achieve isolation between the optical fields. We present simulation results of the hybrid Euler bends and the thermal field distribution. The device is fabricated by e-beam lithography, dry etching, and e-beam evaporation, resulting in a device footprint of ∼ 0.24 × 0.36 mm 2 , with each phase shifter occupying ∼ 0.11 × 0.11 mm 2 . The measured P π of ∼ 1.4 mW is in agreement with the simulations. The extinction ratio is &gt; 28 dB over the C-band due to the highly balanced 2 × 2 multimode interferometer (MMI) coupler used. This device is well suited for the construction of large-scale photonic integrated circuits (PICs) for applications requiring a large number of 2 × 2 optical switches with low crosstalk and low power consumption, such as optical beamforming networks (OBFNs) for microwave beamforming and optical phased arrays (OPAs) for optical beamforming.