Silicon nitride double-tip fiber-to-waveguide edge couplers at visible wavelengths

Silicon nitride fiber-to-waveguide inverse taper edge couplers with double tips are designed and simulated. Double tip edge couplers show a coupling efficiency improvement over single tip couplers at visible wavelengths, which is crucial for loss sensitive quantum optics applications. A loss optimized 2×1 MMI coupler is designed for use as a mode converter in double tip edge couplers.