Up-conversion superfluorescence induced by abrupt truncation of coherent field and plasmonic nanocavity

We theoretically propose a new method for generating up-converted coherent light from two-level systems (TLSs) coupled with a plasmonic nanocavity. The emission spectrum of a TLS excited by a strong laser exhibits a triplet structure called the Mollow triplet. If the lower Mollow sideband is tuned to the cavity mode energy, population inversion of a TLS occurs. When the driving laser is abruptly truncated under this condition, an up-converted photon is emitted from the TLSs. We also predict the up-converted superfluorescence from an ensemble of TLSs as a correlation effect among the excited states of the TLSs.

Single-Molecule Investigation of Energy Dynamics in a Coupled Plasmon-Exciton System

We investigate the near-field interaction between an isolated free-base phthalocyanine molecule and a plasmon localized in the gap between an NaCl-covered Ag(111) surface and the tip apex of a scanning tunneling microscope. When the tip is located in the close proximity of the molecule, asymmetric dips emerge in the broad luminescence spectrum of the plasmon generated by the tunneling current. The origin of the dips is explained by energy transfer between the plasmon and molecular excitons and a quantum mechanical interference effect, where molecular vibrations provide additional degrees of freedom in the dynamic process.