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Optical sources within micro-cavities have been extensively studied for years [1]–[3]. It is today well known that over-coating these cavities with multilayer optics allows to modify their emission patterns in free space in the surrounding media (substrate and superstrate). While sources within single overcoats radiate a quasi-lambertian pattern, more elaborated structures allow to confine the angular patterns in narrow angular or spectral regions. Applications concern lightening and bio-photonics, micro and single photon sources, antennas… However, most overcoats in micro-cavities are classical multilayer designs currently used in the field of thin-film optics, such as mirrors and narrow-band filters, so that one may wonder whether these cavities can be optimized with much more (huge) efficiency. Furthermore, until now the presence of guided waves was not considered in this optimization process. The objective of this paper is to introduce specific techniques to design huge enhancement of emission patterns from micro-cavities. We first introduce zero-admittance layers [4]–[6] in the cavity and show that they also strongly increase (by several decades) in free space the emission pattern. Then we are interested in designing a cavity for which the modal light would largely dominate the free-space light; here we use modal light to designate the light trapped in the cavity and which propagates in the form of guided modes without radiation losses. In order to reach this goal, we show how to design specific poles of the reflection factor in the modal range, that are known to be the modal constants of the layered structure. All results allow to reach a total modal energy much higher than the integrated free-space light, or conversely. Applications may concern micro-lasers, guided waves and lightning, and address the extension of design techniques to the situation of multilayer waveguides.
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