Electrons and photons in mesoscopic structures: quantum dots in a photonic crystal and in a microcavity

Mesoscopic structures with characteristic size either of the order of an electron de Broglie wavelength in semiconductors (1-10 nm) or close to the optical photon wavelength (100-1000 nm) exhibit non-trivial properties due to modified electron or photon density of states. Three-dimensional spatial confinement of electrons in nanocrystals (quantum dots) results in size-dependent energies and probabilities of optical transitions. The photon density of states can be modified in structures with strong modulation of the refractive index in three dimensions (photonic crystals) and in microcavities. Because of the essentially different electron and photon wavelengths, electron and photon densities of states can be engineered separately within the same mesostructure. We report here on synthesis and properties of semiconductor quantum dots corresponding to the strong confinement limit embedded either in a photonic crystal exhibiting a pseudogap or in a planar microcavity. We show that the interplay of electron and photon confinement within the same structure opens a way towards novel light sources with controllable spontaneous emission. Spontaneous emission which is not an inherent property of quantum systems but a result of their interaction with electromagnetic vacuum can be either promoted or inhibited depending on the modification of the photon density of states in a given mesostructure.