Electrically tunable plasmon–exciton strong coupling enabled by qBIC and graphene

Strong plasmon-exciton coupling is usually limited by significant metal losses and strict spectral matching conditions. We present a tunable strong coupling platform by combining the quasi-bound state in the continuum (qBIC) with graphene. By connecting Au nanorod (AuNR) to the qBIC cavity, the plasmon linewidth can be reduced from 245 meV to 18 meV, achieving strong coupling (g = 8.57 meV) with dye molecules, with a splitting of 17.8 meV. By integrating a graphene sheet, the local plasmonic mode (LPM) can be electrically controlled for continuous and reversible tuning, resulting in a resonance shift of approximately 2 nm and enhancing the coupling strength to 11.1 meV.