Effect of angle of incidence on defect modes of symmetric and asymmetric one-dimensional photonic crystals

The impact of the angle of incidence on defect modes within a one-dimensional photonic crystal (PC) containing a central defect has been thoroughly examined. We have considered two distinct types of photonic crystals, each featuring a solitary defect: symmetric PCs and asymmetric PCs. Our findings reveal that in the case of asymmetric PCs, a defect mode emerges precisely at the central wavelength. Conversely, for symmetric PCs, two distinct defect modes appear in the proximity of the central wavelength. By widening the defect layer, these two defect modes can be merged into a single central defect mode. However, it's worth noting that the intensities of these merged defect modes differ from those observed in the asymmetric case. We have analyzed the propagation characteristics of the proposed structure using the transfer matrix method.