A Multilayered Infrared Optical Absorber Based on Epsilon-Near-Zero Metamaterials

In this work, a perfect absorber with metal-ENZ-metal configuration at the wavelength of 1550 nm is presented. The epsilon-near-zero (ENZ) part is a multilayered structure consisting of Au-Ge-Si with a very thin thickness compared to the wavelength; therefore, its optical properties can be determined based on the effective medium theory (EMT) model, which is a homogenization method based on field averaging. The thickness of the layers is adjusted so that the ENZ wavelength occurs at 1550 nm. A square array of nanoparticles is placed on the ENZ structure, which excites the surface plasmon polariton (SPP) at the ENZ wavelength, causing an increase in the electric field and perfect absorption (nearly 100%). It should be noted that the reason for choosing this configuration is to take advantage of the interaction of matter and light in the ENZ wavelength. This absorber is insensitive to polarization and angle of incidence up to 60 degrees and retains almost 90% absorption. The working wavelength of 1550 nm is in the telecommunication window range; therefore, it has a high potential in optical applications such as switching, amplification, and modulation.