Magnetic strong coupling between rectangular hole metamaterials and Fabry-Perot microcavity in THz region

Various studies have so far been conducted on the strong coupling interaction between light and matter in microcavities. Although most of them report on the coupling between the electric field and the electric dipole, the coupling between the magnetic field and the magnetic dipole is rarely reported. In this study, we investigated the strong coupling interaction between a magnetic field and a magnetic dipole using a Fabry-Perot microcavity structure in the THz region consisting of wire grid (WG) mirrors and rectangular hole (RH) metamaterials. Here, the RH is well known as a magnetic current type slot antenna, which can be regarded as a magnetic dipole. To verify this concept, we analyzed the transmission properties of WG, RH, and a microcavity consisting of WG and RH (WGRH) using the transmission line theory. Consequently, we found that in this WGRH, normal mode splitting occurs, and anti-crossing behavior is observed in the dispersion relation. The samples were designed using the finite difference time-domain method and were fabricated via photolithography. We measured the transmission spectrum of the fabricated samples using THz time-domain spectroscopy. Finally, we observed a splitting of the transmission peak owing to mode coupling between the magnetic field and the magnetic dipole in WGRH.