Integrated Magneto‐Optic Circulator on Silicon Nitride for FMCW Transceiver Applications

ABSTRACT Most existing on‐chip coaxial transceiver Light Detection and Ranging (LiDAR) implementations rely on separated transmit/receive architectures, on‐chip 3‐dB power splitting, or external beam splitters and discrete circulators, which introduce limited reception efficiency, excess insertion loss, and additional off‐chip components, thereby significantly hindering system‐level miniaturization and large‐scale integration. Integrated on‐chip circulators represent a key enabling component for highly integrated LiDAR architectures. In this work, a magneto‐optical circulator integrated on silicon nitride (SiN) is demonstrated, and its scattering matrix is systematically characterized. The power‐handling capability of the device is also evaluated, showing that the circulator can tolerate on‐chip optical powers exceeding 200 mW. Furthermore, a Frequency‐Modulated Continuous Wave (FMCW) LiDAR ranging system is implemented to experimentally validate the applicability of the fabricated circulator in integrated LiDAR systems. The integrated circulator represents a promising solution for replacing discrete circulator components in FMCW LiDAR systems, enabling higher levels of system‐level integration and providing practical benefits.