Insertion of a two-dimensional defect into photonic bandgap materials

Abstract

Colloidal crystals with three-dimensional periodicities in the refractive index have a photonic band gap (PBG) in which electromagnetic waves are forbidden. We present a method to fabricate stacked colloidal crystals containing a two-dimensional defect as a middle layer by combining vertical deposition method with Langmuir-Blodgett (LB) technique. The defect layer introduces an impurity mode within the optical stop band, which is observed as a defect peak (pass band) in the optical density spectrum. The dependence of the position of the impurity mode on the size of the defect layer is investigated. It is found that the defect behaved as a donor impurity, as it originates from the bottom of the conduction band. We also study the effect of the sphere size of the surrounding colloidal crystal on the position of defect model through changing the sphere size of the surrounding colloidal crystal with a fixed sphere size of the defect layer.