Large-scale broadband digital silicon photonic switches with vertical adiabatic couplers

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 building blocks have a limited port count (≤8×8) or excessive optical losses (>15  dB). Here, we present a 64×64 digital silicon photonic switch with a low on-chip insertion loss (3.7 dB) and broadband operation (300 nm). The measured switching time is 0.91 μs, and the extinction ratio is larger than 60 dB. The matrix switch with 4096 microelectromechanical-systems-actuated vertical adiabatic couplers has been integrated on a 8.6  mm×8.6  mm chip. To our knowledge this is the largest monolithic switch, and the largest silicon photonic integrated circuit, reported to date. The passive matrix architecture of our switch is fundamentally more scalable than that of multistage switches.