Figure 2
From: Highly efficient dual-level grating couplers for silicon nitride photonics
(a) Schematic of the optimization strategy followed in the design of the dual-level Si–Si\(_3\)N\(_4\) GC; cross-sectional schematic and simulation layout used to maximize the directionality in (b) step 1 and (c) step 2 and the CE in (d) step 3 of the design process.
