Researchers say that combining the nano- and microstructures doubly confines the allowed electronic states. The properties of future devices should, therefore, be very precisely controllable through careful design. They confine electrons and holes in three spatial dimensions and limit them to a very small number of energy levels depending on their size. As a result, they respond very efficiently to those wavelengths of light that correspond to allowed electronic states. Whereas with bulk crystals light can be absorbed anywhere and emitted in any direction, the small number of transitions possible within quantum dots means that they will, effectively, jump when and where they are pushed.
Photonic dots are simply spherical resonant microcavities.
As with the structures used in conventional semiconductor lasers, photons are tightly confined and restricted to oscillating in particular modes. The idea of the Univ. Because the absorption and emission of the quantum dot is extremely efficient and can be controlled very accurately, it can, in turn, precisely excite the WGMs in the photonic dot. This, say researchers, should make possible devices with ultralow lasing threshold, directed emission, or the ability to store light. The upper curve shows the spectrum of the lower left sphere in the bottom part of Figure 1.