Integration of coherent spins in 4H-SiC beam splitters.

The SiCOI (silicon-carbide-on-insulator) platform is a promising solution for integrated quantum photonics. It offers excellent spin-photon interfaces and is compatible with CMOS fabrication processes. Beam splitters are essential in quantum optics, enabling critical operations such as quantum interference and entanglement generation. Most existing spin-integrated beam splitters rely on hybrid integration, where the quantum emitter and beam splitter are made from different materials, leading to efficiency losses. In contrast, SiCOI offers a unique opportunity for monolithic integration, where both the quantum emitter and the photonic device are made from the same material. However, despite the rapid advancements in SiCOI for photonic integration, spin-integrated beam splitters on this platform have yet to be realized. In this work, we demonstrate the integration of divacancy spin defects into SiCOI-based beam splitters, approaching a near 1:1 splitting ratio by tuning the coupling length (Lc). Using photoluminescence (PL) and optically detected magnetic resonance (ODMR) measurements, we confirm the successful integration and coherent control of the spin defects. These results provide initial steps for SiCOI-based quantum photonic circuits, paving the way for future scalable quantum photonic applications.