Theory of spatial confinement of light

A propagator formalism describing the spatial confinement of quantised electromagnetic fields attached to matter is established. Using a non-retarded self-field approach, it is demonstrated that the inherent non-locality of quantum mechanics sets the conceptual limit for how strong a localisation one may achieve. It is argued that so-called superlocalisation of electromagnetic fields accompanies pure spin-1/2 transitions. A new scheme for reaching subwavelength localisation based on phase conjugation of the optical near fields of mesoscopic (or atomic) particles is discussed