Terahertz metamaterial devices: from thickness and material dependence to perfect absorption
MetadataShow full item record
Metamaterials consist of subwavelength unit cells periodically patterned to exhibit extraordinary electromagnetic properties that do not exist in naturally occurring materials. The far-infrared, or terahertz frequency region of the electromagnetic spectrum is ripe with potential with metamaterials providing a promising technological route towards developing application. Metamaterial “perfect absorbers”, typically configured with three layers as metamaterials-dielectric-ground, have attracted tremendous interest due to near unity absorption of incident electromagnetic radiation over a designed frequency range, with the device having subwavelength thickness. Several theories have been developed to understand the physics of perfect absorption. However, it is important to develop alternative numerical and analytical strategies that transparently connect with the electromagnetic and dielectric properties of the constituent materials to better understand how experimentally accessible parameters ultimately determine the absorption. First, this dissertation introduces a metamaterial absorber with air as spacer layer instead of dielectric materials. In the absence of dielectric material loss, the design can achieve three times higher quality factor compared to traditional designs. Additionally, the absence of the spacer material yields the possibility to access the space between the metamaterial layer and the ground plane inspiring a microfluidic channel integrated sensing device with sensitivity more than three times of the reported results. Second, this dissertation investigates the dependence of the metamaterial absorption maxima on the spacer layer thickness and the reflection coefficient of the metamaterial layer obtained in the absence of the ground plane layer. We observed that the absorption peaks redshift as the spacer thickness is increased, in excellent agreement with the analysis. Third, this dissertation presents a detailed analysis of the conditions that result in unity absorption in metamaterial absorbers. These simple expressions reveal a redshift of the unity absorption frequency with increasing loss that, in turn, necessitates an increase in the thickness of the dielectric spacer. Our findings can be widely applied to guide the design and optimization of the metamaterial absorbers and sensors.