Magneto-optical garnets in photonic integration

• YIG is identified as a unique magneto-optical dielectric combining wide bandgap transparency with strong, tunable magneto-optic activity, ideal for integrated photonic applications. • Recent advances in thin-film synthesis techniques have enabled CMOS-compatible YIG layers with nanoscale precision and low optical loss, opening pathways for device-level integration. • Compositional engineering, particularly Bi 3+ doping, significantly enhances YIG’s Faraday rotation, enabling compact nonreciprocal devices for nanophotonics. • YIG plays a growing role in topological photonics, quantum light control, and nonlinear optics by supporting chiral edge states, coherent coupling between magnons and photons, and enhancement due to its gyrotropic properties. • This review highlights the interplay between YIG’s structure, composition, and function, presenting it as a reconfigurable platform for next-generation adaptive photonic systems. Magneto-optical materials with ultralow losses and high thermal and chemical stability are fundamental to the advancement of integrated photonic technologies. Among these materials, yttrium iron garnet (YIG) stands out due to its unique ferrimagnetic ordering, broadband optical transparency, and exceptionally low magnetic damping. These intrinsic properties enable YIG to play a critical role in a variety of photonic applications, including high-density optical memory devices, nonlinear optical systems, and compact waveguide-based modulators. Recent advances in epitaxial growth techniques, chemical doping, and nanoscale patterning have allowed precise engineering of YIG’s magnetic and optical characteristics, facilitating improved device performance, enhanced Faraday rotation, and effective nonlinear interactions at reduced power thresholds. Furthermore, YIG’s compatibility with hybrid integration platforms, such as silicon photonics and superconducting circuits, opens new avenues for multifunctional and reconfigurable photonic architectures. However, low-loss integration with silicon remains hindered by lattice mismatch, thermal expansion differences, and interface-induced scattering that degrade optical performance. Recent studies have addressed these issues through buffer-layer engineering, wafer-bonding approaches, and optimized nanoscale fabrication, enabling reduced propagation losses and improved mode confinement in hybrid YIG-silicon devices. Despite these advances, challenges remain in scalable nanofabrication, minimizing propagation losses in miniaturized geometries, and ensuring environmental stability during operation. Addressing these issues through innovative synthesis protocols, buffer layer engineering, and comprehensive modeling of coupled photon-magnon-phonon dynamics will be essential for transitioning YIG-based components from laboratory prototypes to commercial devices. This review highlights the current state of the art in YIG photonics, summarizes key advances, and discusses future perspectives that position YIG as a foundational material for next-generation classical and quantum photonic technologies.