## 3 Results and Discussion
### Theory Testify  
Next, we performed a full wave simulation to verify the hybridization model used in the proposed graphene absorber structure. Based on the size changing in Figure 4, we provided an analysis of the absorption variations of the absorption peak of the three-ring system, for which sizes of the graphene rings are 0.2 \(\upmu\)m, 0.5 \(\upmu\)m and 1.1 \(\upmu\)m based on the hybridization model. For the full wave simulation, we selected images with frequencies at three absorption peak positions to observe the superposition of the absorption structure. By changing the size of the out SGR, we can clearly find that the coupling hybrid process of the inner double ring and the out ring respectively produces two types of coupling: strong coupling and weak coupling, which directly leads to changes in the absorption peak. In addition, we do not change the outer size of the outer ring (without changing the size of the unite cell), and change the coupling by changing the inner size of the out SGR. When the inner size is reduced (the outer ring size becomes larger), the coupling effect is enhanced, which in turn makes the strong coupling effect stronger and the weak coupling effect weaker, meaning the changes of the two absorption peaks are opposite. Our results are perfectly explained in the hybridization model theory of others [12; 21; 50; 51] discussed previously. Figure 5 depicts the full wave simulation and the electric field distribution at three absorption peak which can perfectly describe the coupling of the structure. The full-wave simulation method is used to simulate the contrast of the field strength. The color for which the field is strong is reddish and the contrast is intensive, while the color being blue means the field is weak. Based on the pointing of the magnetic needle and the full-wave simulation which the FDTD gives, we give the magnetic needle schematic diagram, which can represent the direction and strength of the field. The direction of the magnetic needle represents the direction of the electric field from strong to weak, and the size of the magnetic needle indicates the strength of the field strength at different positions. According to the direction of the magnetic needle, we can give the approximate distribution of the strength of the electric field and the corresponding positive and negative electrodes. We mark \"+\" \"-\" on the edge of the ring using by the magnetic needles. The actual SPP electric field in the ring should remain neutral. Therefore, the up mark and the low mark are symmetrical, so that the total electric field of the ring is neutral. Also, both sign of edges of a ring is identical, so we use a sign (\"+/--\") to represents the electric field distribution near the ring. Based on the full wave simulation, there is no doubt that the three graphene rings coupling at all of the absorption peaks. Utilizing the control variable method, we simulated the full-wave simulation states at different frequencies (two absorption peak positions which Figure 5a is 1.07 THz and Figure 5b is 1.54 THz.) under the same model (the original structure is given in Figure 1), and found that there are two modes of full-wave simulation at two different frequencies. Furthermore, it is explained that changing the size of a single graphene ring structure (the result shown in Figure 4) will cause the two absorption peaks to have different coupling directions due to the existence of coupling, and the change direction of the absorption effect is the same as before. [12; 50; 51; 21] In the electric field distribution, we can find that the electric field is \"+ + - + - -\" in the MPA at the 1.07 THz. Also, the electric field is \"+ - + - + -\" at the 1.54 THz. This perfectly proves the hybridization model theory. Because of the different hybridization modes, the absorption peaks present the different variation trends. As the coupling effect strengthened, the peak of 1.07 THz increased significantly (strong coupling), while the peak of 1.54 THz weakened (weak coupling).