Low-power interlayer directional coupling all-optical switch based on graphene-buried polymer waveguide

Three-dimensional photonic integrated circuits provide a pathway toward high-density optical interconnects in the post-Moore era by vertically stacking functional layers. However, interlayer signal switching in such architectures typically relies on complex electrode layouts, which occupy a large footprint and limit further increases in integration density. To address this limitation, a graphene-polymer hybrid all-optical switch using interlayer directional coupling is proposed. All-optical control is achieved via graphene’s photothermal effect. To exploit graphene’s anisotropic absorption, TE polarization is used for the pump to maximize absorption in graphene, whereas TM polarization is used for the signal to minimize graphene-induced loss. For a 190-μm-long active graphene region, the absorption loss for the 980-nm pump is 8.8 dB, while the loss of the 1550-nm signal due to graphene is negligible. The all-optical switch exhibits a 42.3 dB extinction ratio at 3.8 mW pump power. Furthermore, the rise and fall times are 46.1 μs and 107.2 μs, respectively. Our approach provides one feasible pathway to efficient all-optical interlayer signal switching on a polymer platform and offers a compact, low-power, fast-response integrated component for on-chip multilayer interconnects.