Alternating coupling regimes in a plasmon–molecule hybrid structure through phase–change material

Plasmon–molecule hybrid systems provide platforms for studying light–matter interactions. It is of great interest for systems where both strong and weak plasmon–molecule couplings exit and can transfer into each other freely. In this paper, we proposed a hybrid structure composed by a vanadium dioxide (VO2) layer sandwiched between a polymethyl methacrylate (PMMA) strip array and a gold substrate. The molecular vibration of PMMA interacts with the surface plasmon polaritons (SPPs) of the metal substrate and the coupling regimes can be alternated through the phase transition of VO2. The electric fields at SPP resonances closely relate with the optical properties of VO2. When VO2 is insulator, high electric fields in PMMA strips cause the strong plasmon–molecule coupling and new hybrid modes are formed. When VO2 is metal, the electric fields in PMMA are moderate due to high loss of metallic VO2 and the plasmon–molecule coupling is in the weak coupling regime. The influence of the VO2 layer thickness on coupling properties was also discussed in detail for VO2 in different phases. Our study provides a new strategy to modulate the plasmon–molecule coupling and is inspiring for fundamental and practical researches on light–matter interactions.