Strong interaction between two photons and a plasmon of a complementary metamaterial in a terahertz dual cavity
Fanqi Meng, Mark D. Thomson, Bernhard Klug, Hartmut G. Roskos
Abstract
Guided by Babinet’s principle, we explore strong coupling between the effective magnetic dipole moments of complementary split-slotring metamaterials and the magnetic field of a cavity radiation mode. The strong coupling is demonstrated by a pronounced Rabi splitting of the cavity polariton resonances, corresponding to the ultrastrong coupling regime, with the metamaterial placed at a magnetic-field anti-node of the bare cavity radiation mode, where the corresponding electric field vanishes and no strong interaction was previously observed with a metamaterial consisting of electric dipole resonators. Moreover, exploiting the complementary bandpass/bandstop characteristics of the split-slotring resonators, we realize a dual cavity, coupled via the intermediate metamaterial, and observe strong interaction among two photons and the plasmon in the cavity. When the dual cavity is degenerate, the three-particle interaction collapses to an effective two-particle interaction, where the generalized Rabi splitting is increased by a factor of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msqrt> <mml:mn>2</mml:mn> </mml:msqrt> </mml:math> compared to the single-cavity case involving only one photon and one plasmon. The experimental results are supported both by classical electromagnetic simulations and coupled-oscillator models adopted from cavity quantum electrodynamics.