Light-matter coupling between organic molecules and a THz metasurface

Strong light-matter interactions between confined vacuum fields and matter can lead to the formation of hybridized states called polaritons. In the terahertz (THz) region, these interactions can involve the coupling of vibrational molecular bonds with the resonant mode of a planar optical cavity. We demonstrate an alternative architecture to explore the strong light-matter regime by coupling the plasmonic mode of a metasurface with the sharp vibrational resonance of glucose. More specifically, we gradually increase the number of glucose molecules covering the metasurface and observe a red shift of the plasmonic resonance with a Rabi splitting of 90 GHz at zero detuning. This work is a first step towards the investigation of more complex hybrid cavity architectures combining planar mirrors and metasurfaces to explore multiple polaritonic interactions.