Insertion of a Two-Dimensional Cavity into a Self-Assembled Colloidal Crystal

A planar microcavity has been inserted into a self-assembled colloidal crystal by a combination of convective self-assembly in a vertical geometry and the Langmuir−Blodgett technique. This planar cavity, which is parallel to the {111} planes, induces the appearance of a localized state, a pass band, into the forbidden band gap. We have experimentally determined the optical properties of this defect. The dependence of the position of the localized state is investigated as a function of the thickness of the defect layer. It is found that the defect behaves as a donor impurity, as it originates in the conduction band. Analogously, the crystal surrounding a constant defect layer can be varied. It is also found that the pass band depends on the thickness of the surrounding crystal of the planar defect.