Mechano-optically Co-designed Highly-scalable Silicon Photonic MEMS Switches with Buckling-free 2×2 Horizontal Adiabatic Directional Couplers

Micro-electromechanical system (MEMS) photonic switches based on adiabatic directional couplers (ADCs) potentially offer the advantages including large fabrication tolerance and broad bandwidth, which is essential for large-scale reconfigurable photonic integrated circuits in optical networks and artificial intelligence computing infrastructures. However, the scalability of previous ADC-based MEMS switches is challenging due to the complicated fabrication of vertical ADC switches and buckling-induced performance deterioration of horizontal ADC switches. Here we propose a mechano-optically co-designed 2×2 MEMS switch based on a unique buckling-free horizontal ADC by introducing residual-strain management structures including slab anchors and extra S-bends. For the fabricated device, the waveguide buckling is alleviated significantly and high optical performance is achieved with low loss and low crosstalk over a broad bandwidth of 180 nm. It also features fast switching speed of ~ 2 µs, reliable durability with > 7.2 billion switching cycles, and exceptional scalability with the realization of a 64×64 Benes switch array. The present 2×2 horizontal ADC switches are compatible with all mainstream array topologies and can be fabricated using simple standard silicon photonic foundry processes, which are not accessible for those 1×2 ADC switches reported previously. With these advantages, the present design provides a highly-scalable solution with great potential for MEMS/NEMS photonic devices used in versatile applications.