Optical properties of photonic molecules and elliptical pillars made of ZnSe-based microcavities.

The influence of the geometric shape of optically confining structures on the emission properties of ZnSe-based microcavities is studied. Elliptical as well as coupled circular structures were fabricated with quantum wells or quantum dots as optical active material. For the elliptical pillars a lifting of the polarization degeneracy of the resonator modes is observed as it is favorable to control the polarization state of the emitted photons. The influence of the ellipticity on the polarization splitting of the fundamental mode as well as on the quality factor of the sample is discussed. For the coupled pillar microcavities the effect of their distance on the energy splitting of the fundamental resonator mode is analyzed. Furthermore, detailed measurements of the spatial mode distribution in elliptically shaped pillars and photonic molecules are performed. By comparing these results to the calculated mode distribution their analogy to a diatomic molecule is illustrated. It turns out that the observed mode splitting into localized bonding and delocalized antibonding states in ZnSe-based microcavities is more pronounced for elliptical geometries. The realization of delocalized mode profiles is favorable for the coupling of spatially separated quantum dots.