## 3 Result Analysis  
The absorption of the proposed MA structure is illustrated in Figure 3. Over 90% absorption (nearly perfect absorption) was achieved by the MA in its targeted wavelengths. It achieved an average of 95.3% absorption throughout the wavelengths from 350 to 1250 nm. According to the simulated result, the proposed structure has a peak absorption of 98.2% at 602 nm wavelength. Considering the practical applications, wide bandwidth and high absorption rate are useful indicators when designing an absorber. An absorber must be insensitive to the large incident angle and independent of polarization. The proposed design was simulated and then improved gradually. The materials of the resonating metal surface bear a key influence on the absorption characteristic of the MA, which can be tested by using different materials alternatively. In Figure 4, a comparative study of different metals has been better performed to understand the absorption characteristic of the metamaterial unit cell. Tungsten represents an attractive material for PMA design in the optical spectrum, whereas germanium (Ge), aluminium (Al), and iron show lower absorption. The difference in refraction index of these materials is the reason behind this variation. Gold (Au) shows almost perfect absorption at 400 nm, but after 450 nm, the absorption decreases rapidly. Copper (Cu) demonstrates almost the same absorption characteristics. Figure 4 shows the comparison of different resonating components. For visible and infrared spectrum MA, the absorption and extensiveness of the bandwidth are only slightly affected by the refractive index of the metal [46]. Figure 5 shows the refraction index of  
Figure 3: The Absorption of the MA. As with the materials, the MA's absorption is related to the number of layers [47; 48; 49]. The proposed design is a four-layer MA. The absorption by different layers is shown in Figure 6. It can be seen that the increased number of layers also directly influence absorption. However, the addition of more layers renders the design process complex. As a result, there is a trade-off between layer count and absorption. In Figure 6, in comparison  
Figure 4: Comparison of different resonating components. Figure 5: Refraction index of Tu, Ge, Al, and iron. to the other structures, the final structure can provide a broader absorption bandwidth from 350 nm to 1250 nm. More importantly, the final MA structure covers the optical and near-infrared spectrum with polarization-independent and angle insensitive behaviour. Figure 6 shows the evaluation of the structure. The structure initially had only two layers. A bottom tungsten layer with a thickness of 105 nm and a top silicon dioxide layer with a thickness of 12.5 nm. This initial structure has an average absorption of 50% from 380 nm to 900 nm wavelength. Then, a tungsten bar with a length of 157.20 nm and width of 31.5 nm was introduced on top of the SiO\({}_{2}\) layer. This new structure gave a 65% average absorption. Following this, another tungsten bar with the same length and width was placed on top of the SiO\({}_{2}\) layer. However, this bar is 90\({}^{\circ}\) clockwise rotated, forming a cross-like shape. The structure now starts to show better absorption compared to the previous structures. It has almost 97% absorption at 380 nm wavelength and an average of 80% absorption for the rest wavelength. However, as this layer is a metal surface, it reflects some of the incident light. As a result, this structure cannot absorb as expected. To solve this problem, a layer of SiO\({}_{2}\) has been used to prevent reflection from the body of the metal cross. This gives a peak absorption of 95% from 400 nm to 800 nm. A layer of SiO\({}_{2}\) has been introduced in the final structure to prevent reflection from the top. As a result, 97% absorption from 400 nm to 900 nm was finally achieved. The effect of SiO\({}_{2}\) as an anti-reflection surface will be explained later on in this article.