QUANTUM DESCRIPTION OF THE INPUT AND OUTPUT ELECTROMAGNETIC-FIELDS INA POLARIZABLE CONFINED SYSTEM

The effect on the electromagnetic modes of the interaction with a pola rizable medium confined along one direction is studied in the framewor k of a full quantum-mechanical theory. A general quantum-mechanical me thod of computing the scattered electromagnetic field in confined syst ems is presented. A precise link between the semiclassical and the qua ntum theory of polaritons in confined systems is established. The meth od is applied to the case of a semiconductor quantum well embedded in infinite barriers. The experimental situation of a classical traveling light wave partly reflected and partly transmitted by the well is fou nd to correspond to a particular coherent photon-exciton mixed state. Simple analytical expressions are obtained for experimental quantities such as transmission and reflectivity. The polariton quanta are ident ified as the ''physical'' photons detected in photon counting experime nts.