Multifunctional plasmonic waveguide system based on coding metamaterials and inverse design

The benefits of low-power consumption, high throughput and high parallel processing suggest that optical com-puting has great potential for information processing. In this article, we propose a multifunctional plasmonic waveguide system (MPWS) to implement various optical functions based on metal coding metamaterials and inverse design technology. Due to the flexible and multivariant manipulation of electromagnetic waves with coding metamaterials, the MPWS can be utilized as an ultra-compact multifunctional component in integrated optical processors for optical computing. Because every optical component is designed by a same scheme, the MPWS avoids additional connection loss and waveguide coupling region caused by inconsistent interfaces and footprints. Driven by strong constraint of electromagnetic waves and overcoming the diffraction limit, the size of the core area in MPWS is only 400 nm x 500 nm. To demonstrate the effectiveness of the MPWS, we use it to implement four typical filtering functions and plasmon-induced transparency (PIT)-like effects. Especially, the Q-factor of PIT-like effects reaches to 58.13. Meanwhile, the simulation results optimized by inverse design technology show high consistency with that theoretically calculated by the combination of coupled-mode theory and the transfer-matrix method. Compared to previous works, our proposed MPWS not only provides a universal scheme to implement various optical information processing functions for optical computing but also shows the applications of inverse design on photonic devices.