Figure 2

SEM images.

(a) SEM image of the three-port device. The radii of the two MRRs (R₁, R₂) are 10 μm and 20 μm. The waveguide widths of both bus waveguide and bending waveguide are about 500 nm. The zoom in figures of (b) and (d) are the coupling regions of drop port and through port of R₁ (c) respectively. The coupling gaps of G_L and G_S are 300 nm and 200 nm respectively. (e) and (f) are the zoom in images of the grating coupler and Y-branch, respectively.