Numerical study of the photonic-bandgap effect in two-dimensional slab photonic structures with long-range order

We studied the photonic-bandgap (PBG) effect in two-dimensional (2D) photonic crystal slabs with fabrication-related disorder, by calculating the three-dimensional (3D) photonic density of states (PDOS). For small structural disorder, the PBG bandwidth only becomes slightly narrow, because of the creation of the band-edge-like resonant mode. As the structural disorder increases, the PBG effect is maintained. However, the PBG bandwidth is reduced significantly because of the partially collapsed PBG from the band edge due to creation of the localized mode. When the degree of long-range order (LRO) becomes even worse close to the random structure, lots of localized states are uniformly developed in all frequency ranges of the PBG; therefore, the PBG effect disappears. However, a strongly localized mode still exists because LRO enhances the corrective light scattering. (paper)