Optical Magnetic Field Enhancement by Strong Coupling in Metamaterials

We study theoretically the interaction effects between optical waveguide modes and magnetic resonances in metamaterials, consisting of periodic arrays of paired metallic nanodisks lying on a dielectric waveguide substrate. The plasmon near-field coupling in individual metallic nanodisk pairs results into magnetic resonances. The periodic arrangement of the paired metallic nanodisks can excite optical waveguide modes propagating in the adjacent dielectric waveguide. When optical waveguide modes are close to magnetic resonances by varying the array period, they interact to form two hybridized modes. A coupling model of two oscillators is also proposed to predict well the positions of the hybridized modes. In the strong interaction regime, the hybridized modes have an obvious anticrossing, and thus exhibit an interesting phenomenon of Rabi splitting. Furthermore, the magnetic fields within metallic nanodisk pairs exhibit a huge enhancement, which could find promising potential applications in magnetic nonlinearity and sensors.