Ultrathin photonic absorber with wideband polarization independency characteristics using fractal combinations of ring resonators on ZnSe substrate

We present a combination of split ring resonators for THz absorption applications. This combination creates a fractal organization with an ultra-wideband characteristic between 45.5 and 56.7 THz. During the design process, a very thin ZnSe substrate with a thickness of 0.6 μm was used, and copper resonators were placed on the substrate layer. The back layer was also covered with a very thin layer of copper to prevent the transmission of electromagnetic waves. The proposed design exhibits a wideband absorption characteristic with peak resonance points at 46.36, 47.57, 48.98, 50.39, 52.97, 54.62, and 56.1 THz. Furthermore, the electric field distributions at these peak resonances were obtained to further explore the absorption characteristics. The absorption response was also analyzed for both transverse electric and transverse magnetic modes to demonstrate mode stabilization in the absorption performance. Finally, polarization and angle of incidence variations were studied, and polarization independence was achieved. This design is a promising candidate for THz imaging and stealth applications due to its wideband performance.