Low-power and high-speed 2 × 2 thermo-optic MMI-MZI switch with suspended phase arms and heater-on-slab structure.

We propose a ${2} \times {2}$ thermo-optic switch with high switching performance. The switch is based on multimode interferometer (MMI) couplers and a Mach-Zehnder interferometer (MZI) structure, where the phase arms are designed as laterally supported suspended ridge waveguides (LSSRWs) with a metallic heater placed on the slab. It is experimentally demonstrated that this switch has a power consumption of 1.07 mW, a thermal time constant ${\sim}{4.7};\unicode{x00B5} {\rm s}$, an extinction ratio ${\sim}{30};{\rm dB}$, and an insertion loss ${\sim}{0.5};{\rm dB}$. Particularly, the corresponding figure of merit (FOM) has been improved by 1 order magnitude compared with general thermo-optic switches. This ${2} \times {2}$ thermo-optic MMI-MZI switch may find potential application for network reconfiguration and on-chip optical information processing.