Fig. 1. (a) Scanning electron microscope (SEM) image of the AE-based coupler for the resonator-waveguide coupling system. (b) The cross section of the coupling region and (c) eigen modes in it.

Fig. 2. Intensity evolution along the AE-based coupler. Here, λ=1550nm and, in the analytical model, FEM simulation, and experiments γ=0.

Fig. 3. Spectral responses of the fabricated resonator-waveguide coupling systems with embedded AE-based coupler: (a) under-coupled state, (b) critically coupled state, and (c) over-coupled state. The insets are SEM images. Here, in the analytical model, FEM simulation, and experiments γ=0.

Fig. 4. (a) Lateral PN junction and vertical PN junction applied in the proposed AE-based coupler. (b) The effective self-coupling coefficient depending on the changes of the real part of nDWGeff. (c) Extra coupling loss depending on the changes of the loss coefficient γ. The length L is 200μm for all lines. The MZI is assumed to be balanced.