Super-broadband terahertz absorber: an optimized and magnetized graphene-embedded 1D disordered photonic system

Abstract

In this study, a broadband terahertz absorber was designed and numerically demonstrated. The optical features were computed using 4×4 transfer matrix formalism. The broadband absorption is attained by optimizing the Fermi levels of graphene, the magnetic field, and the thickness of the dielectric layers using the differential evolution algorithm. The results demonstrated that the WMF-optimized scenario offered greater than 90% absorption over a bandwidth of 4.18 THz, and the WoMF&SL scenario provided the shortest bandwidth of 0.89 THz. These findings reveal the significance of the spacer layer to achieve broad absorption. Moreover, the absorption band is tailored to the required spectral range by careful choice of the structural and electrical parameters of the spacer layer; changing the refractive index to 1.2 offers a bandwidth of 4.42 THz and altering the thickness to 12 µm provides a bandwidth of 5.5 THz. The broadband absorption was attained due to the impedance matching provided by the optimized structure over a wide spectral range. Furthermore, the average absorption and bandwidth were enhanced, while fluctuations in the selected absorption band were minimized by engineering the magnetic biasing. The reported super-broadband absorber offers numerous applications in terahertz imaging, terahertz communications, and photodetectors.