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).