## 4 Result Analysis  
The robustness of the designed absorber was analyzed for different oblique incident angles of EM waves (both TM and TE polarization). The incident and refraction angles have a substantial impact on the reflection coefficient. The polarization angle (phi) and oblique incident angle (theta) of the incident EM wave on MMA is illustrated in Figure 6, where EM wave propagation is towards the negative z-axis. The green half-circle indicates the 180\({}^{\circ}\) oblique incident-angle area of EM wave theta (\(\theta\)), and the blue circle shows the 360\({}^{\circ}\) phi (\(\phi\)) angle area of EM wave components such as electric and magnetic field vectors. The oblique incident angle's stability and absorption level of the designed MMA were analyzed by changing the oblique angle incidences from 0\({}^{\circ}\) to 90\({}^{\circ}\). The absorption property for the oblique incident angle of TM and TE polarization are revealed in Figure 7. A high absorption at normal incident \(\theta=0^{\circ}\), and a minor variation is observed in absorption level at low oblique incidents up to \(\theta=30^{\circ}\) for both polarization. However, for the larger oblique incidents (\(\theta\geq 40^{\circ}\)), the absorption of TE polarization starts fluctuating, as shown in Figure 7a. On the other hand, the absorption plot of TM polarization for oblique incidents is shown in Figure 7b. Apart from fluctuations, high absorption is still maintained by designed MMA up to 90% for the total bandwidth at oblique incidences from 10\({}^{\circ}\)-40\({}^{\circ}\). It goes down from 90% at \(\theta\geq 50^{\circ}\); however, designed MMA shows over 70% absorption for the TE wave polarization and maintains over 85% absorption for TM wave polarization. This indicates that the proposed Ni-AlN-Ni-based MMA is suitable for various applications due to its stable absorption of 70% at different oblique incident angles. The polarization-angle insensitivity is also an expected performance index in the applied application fields. The proposed MMA shows polarization-angle (\(\phi\)) insensitivity due to its rotational symmetrical patch structure. Figure 8a,b show the absorption curve of various polarization angles for TE and TM polarization. The polarization angles varied from 0\({}^{\circ}\)-180\({}^{\circ}\) by increasing 30\({}^{\circ}\). The MMA shows a uniform absorption, and no fluctuation is observed for various polarization angles (\(\phi\)) for both TE and TM polarization. Therefore, the proposed Ni-AlN-Ni-based MMA achieved a broad absorption band by fulfilling the polarization-independent condition. The magnetic field \(\left|\overset{\rightarrow}{H}\right|\) and electric field \(\left|\overset{\rightarrow}{E}\right|\) density of TE polarization for different wavelengths are presented in Figure 9 to understand the absorption behavior of the projected MMA. Figure 9a-d illustrates the electric field at wavelengths 380 nm, 1440 nm, 2000 nm, and 2500 nm, respectively. As the operating wavelength increases, the electric-field density increases like a vertical dipole-shape pattern. It shows the high electric-field intensity on both sides of the hexagonal ring-shaped resonator. A potential electric-field  
Figure 5: The performance investigation of the designed metamaterial absorber for different substrate materials. density is observed towards the outer ring at higher wavelengths, which leads to high absorption due to the surface plasmon polariton. This phenomenon happens because the outer ring is responsible for higher absorption at the upper wavelength region. The surface plasmon happens due to the conduction of electrons between dielectric and metal at the surface, where it conducts strongly with electromagnetic radiation. Also, the electric field intensity is particularly confined on the outer hexagonal resonator and observed a dipole-type pattern. Thus, the smooth electric-field distribution between the hexagonal ring-shaped is formed by the mutual coupling of multiple Plasmon's.