Tunability of absorption with temperature in the terahertz regime based on photonic crystals containing graphene and defect InSb layers

Abstract

We show that the absorption of graphene layers included in InSb layers as the defect of photonic crystals can be significantly enhanced. This effect is due to the field localization in the defect layer at particular wavelengths. For normal incidence, we first consider the case at which the InSb-graphene layer-InSb layers are sandwiched between two photonic crystals with the same and different numbers of unit cells at each side. It is demonstrated that the position of absorption peak of the graphene layer can be tuned by varying the ambient temperature in the terahertz regime under normal incidence. The absorption peak shifts toward longer wavelengths with decreasing temperature. The values of absorption peaks also depend on the temperature. It is demonstrated that complete absorption can be obtained in this structure at specific temperatures and optimized number of unit cells. Our results also indicate that the distance between absorption peaks decreases while their numbers increase with increasing the thickness of InSb layers at a fixed temperature. The absorption of graphene layer depends on its position in the structure and incident angle. Tunable absorption with temperature is also studied in the vicinity of a larger wavelength for both TM and TE polarizations. By including the absorption of InSb layer in the calculations, it is shown that the contribution of InSb and graphene to absorption depends on temperature and thickness of InSb layers.