Phase-shifted response of plasmonic nanostructures: Implications to luminescence upconversion

We analyze the dynamics of a quantum dipole emitter (QDE) illuminated by a resonant electromagnetic field and placed close to a metal nanostructure, whose response to the incident field is phase shifted by 3π/2 (-π/2). It is found that, due to the phase shift in a field scattered by the nanostructure (and acting on the QDE along with the incident field), QDE dynamics is characterized by a fast QDE transition to the excited state followed by relaxation to a stable superposition (of the excited and ground states) with a close to 1 probability of the QDE to be found in the excited state. We further argue that this effect can advantageously be used for luminescence upconversion enhancement when being realized for a lower excited state in the energy transfer upconversion process since, by largely eliminating the radiative relaxation channel, the probability of excitation transfer will be increased.