Grating-assisted vertical couplers for signal routing in multilayer integrated optical networks

•We propose a simple and efficient design procedure for grating assisted vertical couplers.•The design criteria for grating‐assisted vertical couplers are highlighted.•The proposed devices enable three‐dimensional routing in multi‐layer optical networks on chip.•Multiple grating‐assisted vertical couplers can be connected into higher order routing matrices.

Grating-assisted vertical couplers, which behave as add-drop filters, are proposed for wavelength routing of the signal among the different layers of on-chip multilayer optical networks. The device implements a 2×2 wavelength router which can be assembled into higher-order three-dimensional matrices. In particular, simple design criteria are found through a rapid and efficient optimization approach based on the mode analysis and demonstrated by the Finite Difference Time Domain (FDTD) simulations. The proposed numerical method is valid either for in-plane or for vertical grating-assisted couplers and it requires negligible computational effort. Different configurations of grating-assisted vertical couplers are designed and their spectral behavior is analyzed by the FDTD. The proposed devices achieve low values of the crosstalk between the different ports (below −20 dB) and of the input reflection (below −15 dB).