Engineering magnons in YIG-based heterostructures - from strong coupling to short wavelength modes

Magnetic insulators such as yttrium iron garnets (YIGs) are of paramount importance for spin-wave or magnonic devices due to their ultralow power dissipation, exotic magnon state, and coherent coupling to other wave excitations. Magnetic insulator heterostructures bestow superior structural and magnetic properties and house many novel properties due to their strong and engineerable exchange interactions between individual layers. In this talk, I will discuss several YIG-based heterostructures in the context of strong magnon-magnon coupling, which enable a variety of coherent coupling phenomena, such as the magnonic-induced transparency, short wavelength excitation and selectivity, and nonlinear magnonic couplings. Finally, I will move from the conventional metal-insulator systems to a recently reported, all-insulating system exhibiting strong magnon-magnon hybridization. The versatility of magnon-magnon coupling in such heterostructures can prepare tailored magnon modes for their further hybridization with other solid-state excitations, including but not limited to optical photon, phonon, and qubits.