Controlled spontaneous emission of a tri(8-hydroxyquinoline) aluminum layer in a microcavity

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Abstract
We report the fabrication of all-dielectric microcavities with a tri(8-hydroxyquinoline) aluminum (Alq3) organic layer as the emitting layer. In a first step, we characterized the materials used in the structures by ellipsometry, and ensured nondegradation of the organic material in the fabrication process. Then, by angular-resolved photoluminescence, we investigated changes in the angular emission pattern caused by the cavities and observed a sharply directed emission. We also investigated the influence of the position of the radiative layer in the cavity on normal spontaneous emission. We observed enhancements in spontaneous emission over 20 times higher than that of a single Alq3 layer. These are the highest reported for organic material based microcavities. They are mainly explained by the very small thickness of the Alq3 layer (20 nm≡0.06λ, λ being the resonant wavelength), by high-quality low-loss dielectric mirrors as well as by the narrow collecting angle of our experiment (±3°). This study corroborates analogous works and demonstrates the possibility of controlling the spontaneous emission of an emitter by a microcavity.