Large-scale photonic switches are essential devices for energy- and cost-efficient optical communication networks in cloud and data-intensive computing. Silicon photonics is an attractive platform for high-density photonic integrated circuits with low manufacturing costs through the leveraging of existing advanced complementary metal-oxide-semiconductor processes. Many optical components such as lasers, modulators, splitters, and photodetectors have been successfully integrated on silicon; however, the quest for large-scale silicon photonic switches has remained elusive. Previous silicon photonic switches made of cascaded 1×2 or 2×2 switching stages have a limited port count (≤8×8) or excessive optical losses (>10  dB).
In this talk, I will present highly scalable silicon photonic switches enabled by microelectromechanical systems (MEMS). The extremely high extinction ratio (> 60 dB) of the MEMS-actuated switching elements eliminates the optical loss accumulation of multistage switches. The compact size of silicon photonic MEMS enables reliable switching operation with fast switching speed (< 1 μs) and low switching energy (~ 10 pJ). I will present the experimental demonstration of a 64×64 matrix switch with 4096 MEMS-actuated vertical adiabatic couplers integrated on a 7 mm×7 mm chip. This is the largest monolithic switch, and the largest silicon photonic integrated circuit, reported to date. The passive matrix architecture of this switch is fundamentally more scalable than that of multistage switches.