1. UKM Learning and Research Repository
2. Master Thesis / Tesis Master
3. Faculty of Science and Technology / Fakulti Sains dan Teknologi

Title:	Development of metasurface based electromagnetic absorber for microwave region and polarization conversion in terahertz region
Authors:	Tamim Ahmed Mahfuz (P94718)
Supervisor:	Mohammad Rashed Iqbal Faruque, Assoc. Prof. Dr.
Keywords:	Metasurfaces Electromagnetic Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	22-Jul-2021
Description:	Metasurfaces are sub-wavelength scale (˂ λ/4), two-dimensional (2D) periodic structure that can be engineered to achieve any desirable functionalities. Metasurface has the potential to replace bulky optical components and devices as they are ultra-thin, lightweight, able to provide new functionalities and overcome the limitations of the conventional 3D metamaterials. In this thesis, a metasurface absorber is designed and developed for microwave frequency applications. Moreover, a metasurface is also proposed and numerically explained as highly efficient polarization conversion at far-infrared frequency spectrum. Structural design, optimization, and results examination of the absorber and polarization converter are carried through the CST microwave studio electromagnetic simulator. The performance of the absorber is analyzed according to the theory of equivalent medium model. The co-polarized and cross-polarized reflectance coefficients of the polarization converter is described by interference theory, where two different medium and interference layers are considered with the reflected and transmitted wave. At first, the fundamental physics of strong interactions between the light and metasurfaces are briefly discussed. Then, a digital metasurface absorber that is developed by binary coded unit cells, and the combination of coded unit cells leads to excellent polarization insensitiveness, symmetrical characteristics, polarization conversion, and perfect absorptions is presented. The binary patters '0' and '1' coded arrangements [00, 01, 10, and 11] are shows the digital characteristics by high electric and surface current concentration at '1' position and vice versa for '0' position. The simulated results show an absorptance peak at 11.37 GHz, 15.75 GHz, and 18.76 GHz, whereas the absorptance are around 97%, 99%, and 94%, respectively. The theoretical and experimental results are consistent with the simulated results despite slight decreases in absorption due to the effect of cross-polarization and the free space measurement system. In addition, the polarization conversion metasurface shows efficiency over 90% from 282.9 to 302.3 µm (0.987~1.062 THz) and 558.78 to 676.7 µm (0.442~0.537 THz) showing multiple resonances at 286.7 µm, 298.25 µm, 586.1 µm, and 689.55 µm. Finally, the performances and diverse characteristics of the designed metasurface based electromagnetic absorber and polarization converter show potential applications in microwave frequency and terahertz frequency applications, respectively,Sarjana Sains
Pages:	131
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.