[Springer] Spot Size Converters for Enhanced Coupling Efficiency Between Single Mode Fibers and High-Confinement Si3N4 Waveguides Copy

For highly loss-sensitive applications of photonic integrated circuits (PICs), efficient coupling of high-confinement silicon nitride (Si3N4) passive waveguides with active optoelectronic components and standard single mode fibers (SMF) is important. To achieve this, width and height of the waveguide are varied to enable polarization-independent low-loss coupling. A mode-field converter is realized by focused ion beam etching, and a proof of concept is provided with three different prototypes that differ in their final spot size and are fabricated by focused ion beam milling. For these prototypes, a broadened mode field diameter and a more efficient coupling to a SMF are demonstrated.