Excitation of near field coupled dual toroidal resonances in a bilayer terahertz metamaterial configuration

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We discuss the excitation of dual toroidal dipolar resonances in a bilayer terahertz metamaterial configuration and examine their near field coupling induced modulation. The study is focused on the interaction and modulation between toroidal resonances excited in two layers of a bilayer system. The rotation of the symmetric circular split ring of the top layer resonator with respect to the bottom one, causes the dual resonances to modulate and ultimately switching into a single toroidal resonance. The strong near field coupled modulation is observed when both the resonator layers are placed in close proximity. A Lagrangian approach is suggested to understand the underlying mechanism of the coupled toroidal resonances. The increase in strength of the toroidal dipolar resonance on adding two layers is suggested based upon the quality factors of the resonances. Such a study enables the design of toroidal photonics devices with high quality factors and improved light–matter interaction.