Near-infrared absorbers based on the heterostructures of two-dimensional materials

Although the conductance and dielectric function of graphene can be tuned by applying external voltage, the tunability is less than 3%. Hybridizing graphene with other two-dimensional transition metal dichalcogenides (TMDs) can improve the adjustability and tunability of the optical properties of graphene-based structures at near-infrared frequencies. In this paper, we theoretically compute the dielectric function of graphene-MoTe2-graphene and graphene-MoTe2-graphene heterostructures utilizing the quantum electrostatic heterostructure (QEH) model, which is an ab-initio method. Utilizing the QEH results, we propose a hyper crystal (HC) absorber at near-infrared frequencies. Hence, we use the transfer matrix method to investigate our proposed absorber analytically. Moreover, we simulate the graphene-TMD-graphene (G-TMD-G) absorbers by the numerical finite difference time domain method. The results of the numerical solution are consistent with those of the analytical method. Due to the dependency of the Fermi level of graphene on the direct bandgap of the TMDs, the dielectric function of the G-TMD-G heterostructure can be tuned and enhanced further by changing the number of TMD layers. Finally, we demonstrate that the full absorption of the heterostructures can be achieved at different frequencies for transverse magnetic polarization. Since the thicknesses of the layers in the HC are lower than the wavelength of the light, no diffracted bands are ubiquitous, and the absorption can be observed for a wide range of incidence angles and bandwidths at near-infrared frequencies. Because of utilizing graphene-based HCs, in addition to the feasibility of design compared to the complex metasurfaces, the absorption bandwidth is significant for a wide range of incidence angles. This kind of HC absorber can be used in the design of sensitive optical devices, such as tunable filters, detectors, and photovoltaic applications.