Electromagnetic power provided by sources within multilayer optics: free-space and modal patterns

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Abstract
An electromagnetic theory is presented that makes possible the development of a complete energy balance within an arbitrary multilayer microcavity that supports different kinds of classical optical sources. The theory is based on a single Fourier spectrum of waves and is valid for transparent or dissipative stacks, with no use of modal methods. We show how the power provided by the cavity is converted into Poynting flux and absorption. Free-space and guided-mode patterns are calculated for single layers, mirrors, and narrow-band filters. The modal pattern is shown to be strongly dependent on the cavity poles. Discretization of the high-frequency energy into a set of guided modes is introduced as an asymptotic limit of the problem when absorption vanishes to zero. The applications concern defect-induced absorption in optical multilayers or guided-mode coupling through microirregularities in a stack, as well as spontaneous emission in classical microcavities.