## 2 Design and Simulation  
Firstly, a metamaterial structure was designed based on the combination of traditional Cut Wire (CW) resonator as bright mode and a pair of U-Shaped Split Ring (USR) resonator as dark mode. Two of the USRs were on the same side of CW and were symmetrically distributed up and down to form a unilateral symmetric structure, as shown in Figure 1a. In order to achieve the EIT-like window at certain wavelength band, the software, CST Microwave Studio was used to calculate the electromagnetic field of metamaterial by optimizing various parameters, including the length of CW structure \(L\), the width of CW \(w_{1}\), two side lengths of USRs, \(a\) & \(b\), as well as the width of USRs \(w_{2}\). The period of metamaterial unit was set as \(P_{x}=P_{y}=120\)\(\upmu\)m. Each base structure consisted of a substrate material as the lower layer and a metallic material with a special structure as the upper layer. The substrate was made of lossless quartz with a dielectric constant \(\epsilon\) of 3.75 and a thickness of 20 \(\upmu\)m was utilized. A 200 nm gold layer with a conductivity \(\sigma\) of 4.6 \(\times\) 10\({}^{7}\) S/m was selected to better form the bright and dark mode to realize the EIT effect. The size parameters of \(L\), \(a\), \(b\), \(w_{1}\) and \(w_{2}\),were set as 90 \(\upmu\)m, 40 \(\upmu\)m, 30 \(\upmu\)m, 6 \(\upmu\)m, and 4 \(\upmu\)m, respectively, while the coupling distance \(\delta_{x}\) and \(\delta_{y}\) were fixed as 4 \(\upmu\)m and 30 \(\upmu\)m. For the design of the asymmetric metamaterial structure, the upper and lower USRs were asymmetrically distributed with respect to the transverse central axis, as shown in Figure 2a. The coupling distance \(\delta_{xup}\) between the CW and the upper USR was set to be 13 \(\upmu\)m, and the coupling distance \(\delta_{xdown}\) between the CW and the lower USR was set to be 4 \(\upmu\)m, other parameters remained unchanged as the symmetrical structure. The CST simulation used a frequency domain solver with a tetrahedral mesh, and the boundary conditions in the \(x\) and \(y\) axes both used the unit cell, while the z direction was set as open (add space) and the Floquet mode is set as 2. The incident terahertz wave was set to be vertical with respect to the surface of the metamaterial to explore the transmission characteristics of the EIT-like effect. Figure 1: The transmission properties of metamaterials based on different symmetrical structures. (**a**) Schematic diagram of metamaterial structure; (**b**) The transmission spectra of CW (black), USRs (blue), and CW+USRs array (red) in the direction of \(E_{y}\) electric field. The CW resonator shows typical LSP resonance at 1.01 THz, while an electromagnetically induced transparency-like window can be found in the CW + USRs structure; (**c**) The transmission spectra of USR array in the direction of \(E_{x}\) and \(E_{y}\) electric fields, the horizontal orientation of the incident electric field can excite the LC resonance of USRs at similar frequencies. Based on the designed symmetrical structure, three groups of metamaterials were analyzed. The first group of metamaterials consisted of CW resonator arrays only, the second group of metamaterials consisted of USRs array only, and the third group consisted of both the CW and USRs structures. The normalized transmission spectra of the three metamaterial groups are shown in Figure 1b. It can be seen that the CW resonator array shows a typical local surface plasmon resonance (LSP) at 1.01 THz, indicating that as the incident electric field is parallel to the CW, the electromagnetic radiation can be directly coupled into the CW; however, since the incident electric field is vertical, it becomes ineffective for USR excitation under the same frequencies. In Figure 1c, it can be found that the horizontal direction of the incident electric field can excite the LC resonance of USRs at similar frequencies.