A Highly Stable Perfect Metamaterial Absorber Based on the Plasmonic Effect of Metamaterial Nano-cells for Optical Spectrum Applications

The exploitation of optoelectronic components and devices in the visible to infrared (NIR) spectrum requires unique electromagnetic qualities, which makes the choice of the size and shape of such a structure a main factor in having a stylish and crucial design. In this chapter, a near-perfect metamaterial absorber (PMMA) is proposed with numerical analyzes for applications in the visible to NIR regime. Our design technique is based on the optimization of the electromagnetic (EM) qualities of the studied unit cell (often concerns the choice of material, shape and dimensions) so that it is suitable for the desired applications. This cell with a period \(P\) of 350 nm is designed according to the metal–insulator-metal (MIM) configuration of three layers stacked one above the other for a total thickness of 100 nm. The metal representing the top and bottom layers is tungsten (W), while the dielectric representing the intermediate layer is titanium-dioxide (TiO2). The patch (of nanometric dimensions) of the unit cell is constituted by two inner and outer square-shaped rings loaded with four slotted circles each. The study of the proposed absorber is carried out on the wavelength spectrum ranging from 400 to 1400 nm, its analysis concerns reflection and absorption. Subsequently, the electromagnetic behavior of the PMMA is discussed based on the nature of its polarization, surface current, refractive index, and also based on the proposed equivalent electric circuit model. Based on the obtained simulation outcomes, the proposed PMMA has crucial performances; this is evident through the high absorption rates (near unity) obtained over the entire visible and near-NIR spectrum. An average absorption of around 92.32% is also obtained on the same spectrum thanks to the plasmonic effect of the unit cell, more particularly to the shape and thickness of the cell patch. On the other hand, a careful study of the properties of the incident EM waves propagating in our absorber allowed us to note its insensitivity to polarization for both transverse electric (TE) and transverse magnetic (TM) modes. Furthermore, the incidence of these waves on the top face of the patch in an oblique manner does not affect the absorption characteristics up to the angle of 60°, which justifies the stability and robustness of our PMMA. Finally, and thanks to its simple design, our absorber can be used in several applications related to optical windows such as the harvesting of solar energy, the development of the electrical qualities of optical filters, and the miniaturization of photodetectors.