QUANTUM DOTS OF LIGHT

Abstract

Basic ingredients of a microscopic theory describing the degenerate four-wave mixing of the outgoing field from a mesoscopic source particle were established. Starting from many-body theory and selfenergy quantum electrodynamics it is argued that the best spatial confinement one might hope to obtain of the source field is given by the extension of the transverse part of the current density distribution induced in the mesoscopic particle. Taking into account the phaseconjugation of evanescent components of the source field, the existence of so-called quantum dots of light having a subwavelength extension is predicted. Using the outgoing field from the tip of an optical near-field microscope in combination with a phaseconjugating mirror exhibiting a sufficiently long memory time light dots can be made experimentally. A new nonlocal nonlinear response tensor enabling one to study the four-wave mixing process of the local field itself is presented.