Spontaneous emission in multilayer microcavities: modal theory extended with Fourier-Green analysis for dissipative structures

Two rigorous theories are presented and compared to describe the interaction with the electromagnetic field of localized sources confined within microcavities. Both the light which can escape the structure and the embedded radiation are taken into account by these formalisms. The modal theory describes the field in terms of modal functions and is limited to lossless structures. On the other hand, the Green approach can naturally cope with lossy cavities and considers the coupling of the sources with a continuum of waves with spatial frequencies ranging from zero to infinity. The two theories are compared and the consequences of losses are investigated in the case of a current source located in the spacer of a resonant multilayer structure. It is shown that the modal theory gives correct predictions when the imaginary part of the refractive index is as large as , whereas the Green approach becomes necessary to describe the emission in lossy structures. In this last case, we show that the spontaneous emission factor is not strongly affected by losses, although the emitted power is decreased due to absorption.