Abstract: The condensed electromagnetic field of localized surface plasmon mode in metallic nanocavities brought new opportunities in studying the strong light-matter interaction. Under certain conditions, the rate of coherent energy exchange between a cavity photon and an electronic transition surpasses its fundamental energy dissipation rates, which is defined as the strong coupling regime. This process may generate a part-light part-matter quasi-particle, which is known as a hybrid polariton. A series of recent works in quantum optics is summarized, particularly on studying the strong coupling phenomenon and its dynamic control in plasmonic systems, such as strong coupling between metallic nanocavities and chiral J-aggregates, fine-tuning of polariton energies near zero-detuned point, and active control of excitons strongly coupled to plasmonic nano-cavities using a microfluidic technique. Exploring the active control of the optical field on a sub-wavelength scale is valuable, which benefits the miniaturization of optoelectronic devices. Strong coupling systems possess wide application prospects, such as quantum information processing and ultra-sensitive biochemical detections.

Key words: localized surface plasmon polaritons, excitons, chirality, strong coupling, active control