All-optical router through dynamically controlling the distribution of electron concentration in indium tin oxide

We report an all-optical router in a hybrid trilayer platform integrating a metallic nanostructure, a dielectric spacer, and a routing control layer. The structure utilizes pump light at different wavelengths to selectively excite localized surface plasmons (LSPs) in metallic nanostructures, which are of various heights, generating drastically enhanced electric fields to dynamically modulate the electron concentration distribution within the indium tin oxide (ITO) waveguide in the routing control layer. Consequently, the propagating surface plasmon polaritons in the waveguide are directed to different output ports due to their distinct propagation losses, achieving a high-performance all-optical router. Numerical simulations demonstrate that the proposed router achieves extinction ratios of 32.7 dB and 39.1 dB at excitation wavelengths of 1640 nm and 1760 nm, respectively, with a compact footprint of only 15 μm × 12 μm × 8 μm. More importantly, this study provides a pathway to ultralow-power all-optical routing by synergistically leveraging the drastically enhanced field of LSPs and the third-order nonlinear response of ITO in the epsilon-near-zero region.