Spatio-temporal description of the origin of optical-near-field interactions

Optical-near-field interactions occur via virtual photons that are non-resonant with the nanomaterials. Since the virtual photon exists only on a timescale shorter than the timescale of the interaction between the propagating light and the nanomaterial, the optical-near-field interactions exhibit non-Markovian temporal properties. We propose the spatio-temporal description of excitation transfer dynamics via virtual photons, and clearly show that the spatial properties of optical-near-field interactions at a short distance originate from the non-Markovian temporal properties on short timescale. Thus, the origin of optical-near-field interactions can be understood using the spatio-temporal description of the non-Markovian dynamics.