Fig. 1. Coupler structure

Fig. 2. Cross section of ridge waveguide

Fig. 3. Distribution of fundamental mode field

Fig. 4. Coupling transmission diagram of different spacing S

Fig. 5. Coupled transmission diagram of different tapered waveguide length L₂

Fig. 6. Coupled transfer diagram of different substrate thickness h

Fig. 7. Simulated electric field transmission distribution

Fig. 8. Broadband transmission of tapered coupler