Broadband photon–magnon coupling using arrays of photon resonators

Abstract

We studied the broadband characteristics of photon–magnon coupling (PMC) between a yuttrium iron garnet (YIG) film and arrays of inverted split-ring resonators (ISRRs). To achieve photon–magnon interaction available in a wide frequency range, we optimized the geometries and dimensions of single ISRRs and their array structure by numerical simulations in order to manipulate the resonance frequencies, bandwidths, and signal gains. With those optimal ISRRs arrays, we then experimentally observed multiples of anti-crossing regions between the YIG's magnon mode and the coupled photon modes from |S₂₁|-vs-frequency measurements under different strengths of externally applied static magnetic fields. It was found that the bandwidth of photon–magnon interaction increases up to Δƒ ∼ 2 GHz for the number of ISRRs with N = 4. On the basis of an electromagnetic classical model, we analytically derived coupling between a photon's multiple resonance modes and the magnon mode in broad-range frequencies, the data on which is in good agreement with the experimental observation of the anti-crossing dispersions of the ISRR–array–YIG hybrid. This robust hybrid system provides for more reliable control not only of multiples of photon and magnon couplings in a wide range of operating frequencies but also of the net coupling strength variable in the 30–90 MHz range at room temperature. This experimental finding reveals the potential for development of a new class of wideband resonators and offers guidelines for the optimal design of planar-geometry, broadband photon–magnon devices.