Interação da luz com meios contínuos: abordagens clássica e quântica

Abstract

In this thesis we study some fundamental aspects related to the interaction of electromagnetic radiation with continuous media. In the first part of the thesis, we propose a division of the energy density, of the momentum density and of the energy flux of classical electromagnetic waves in linear non-absorptive media into electromagnetic and material parts. The electromagnetic part has the same form independently of the medium when written as a function of the averaged electric and magnetic fields, without an explicit dependence with the properties of the medium.The material part is calculated directly from models adopted for the material media and the consistency of the division is verified through a series of examples. We believe that the forms that we propose for these physical quantities, although make the same experimental predictions than other proposals, are the most natural and intuitive forms, elegantly inserted in the fundamental concepts of classical electromagnetism.In the second part of the thesis, we present an extension of the photon wave function formalism introduced by Bialynicki-Birula and Sipe that includes the interaction with continuous media, which results in an alternative way for describing the quantum interaction between light and matter. As an example of application of the formalism, we calculate the quantum state of the twin photons generated by parametric down- conversion in agreement with previous treatments, but with a more intuitive interpretation.