# Infrared All-Dielectric Metasurface Beam Splitter Based on Transflective Structures
## 3 Simulation Results
(**d**) The intensity of the Y\(-\)Z plane at the transmissive end of the metasurface beam splitter under the incoming y-polarized light at 1.55 \(\upmu\)m.  
As shown in Figure 5, the nanocolumn's additional phase shows almost no change to different linear polarization lights. Due to the fact that circular and elliptical polarization lights can be decomposed into two orthogonal linear polarization lights, the nanocolumn could maintain the polarization characteristics of the arbitrary polarization beam. As shown in Figure 6, the splitting ratio changes from 59%:41% to 48%:52% with the variation of the polarization angle. This is due to the fact that although the individual metasurface unit cell is polarization-independent, the splitting ratio variation arises because of the spatially polarized difference in the X and Y directions for the overall structure after the arrangement. It also conforms to the characteristics of the BS device, which is sensitive to the angle of incident polarization and changes the splitting ratio without changing the polarization of the outgoing light. Figure 5: The verification of the polarization-maintaining performance of the nanocolumn. Figure 6: The variation of transmittance and reflectance with the polarization angle. To investigate the operation of this metasurface under other size conditions, we used the designed 5 \(\upmu\)m \(\times\) 5 \(\upmu\)m metasurface as a benchmark and combined four such metasurfaces into a 10 \(\upmu\)m \(\times\) 10 \(\upmu\)m metasurface array. Eventually, an isophase plane tilt circumstance appears at the transmissive end of the metasurface, as shown in Figure 7. This shows that different-sized metasurface arrays are likely to be constructed to match different-sized application conditions. In order to calculate the double-ended outgoing angle, we normalized the intensity distribution near the maximum of the outgoing light field intensity along the \(y\)-axis and calculated the corresponding emergence angle, and the results are shown in Figure 8. The angle of emergence at the transmissive end is 9.2\({}^{\circ}\), and it is 8.8\({}^{\circ}\) at the reflective end. According to Equation (3), the expected inclination angle of the isophase plane is 83.6\({}^{\circ}\), and the propagation angle perpendicular to the isophase plane is 6.4\({}^{\circ}\), which is similar to the simulation measurement results; at the same time, it is known that the maximum design deflection angle is 26.5\({}^{\circ}\), which is reached when the additional phase difference is 2\(\pi\). The maximum deflection angle may be modified in the actual design by considering the metasurface material, the unit cell period, and the working waveband, all of which have certain design flexibility. Figure 8: The double-ended normalized intensity distribution at different emergence angles. Figure 2:0 The isophase plane at the transmissive end of the metasurface array under the incident x-line polarized light, with white arrows in the direction of the isophase plane vertical line, a black dashed line being the light-emitting surface of the metasurface, and different color stratifications representing different isophase planes. The tolerance of incident light angle change is an important performance indicator of beam splitters. Figure 9 simulates the double-ended isophase plane at various angles of the metasurface by continuously changing the incidence angle and then determining its operating angle bandwidth; isophase plane tilt effects are demonstrated at 0\({}^{\circ}\)\(\sim\)15\({}^{\circ}\) with the same effects as Figures 3 and 4. When the incident angle increases to 16\({}^{\circ}\), the reflective end does not exhibit the expected isophase plane tilt effect, as shown in Figure 9a.