# Infrared All-Dielectric Metasurface Beam Splitter Based on Transflective Structures
## 3 Simulation Results  
When the light source is an x-polarized plane wave incident on the metasurface face along the positive z direction, the transmissive end and reflective end of the metasurface beam splitter exhibit an obvious isophase plane tilt phenomenon at 1.55 \(\upmu\)m wavelength x-line polarized light (i.e., TE light) incidence, as shown in Figure 3, while the ratio of metasurface transmittance to reflectance is measured as 59%: 41%, which is close to the 1:1 splitting ratio. Figure 3c,d show the incidence using y-line polarized light (i.e., TM light) of the same wavelength. They demonstrate an effect of isophase plane tilt, like x-line polarized light. Since the light emission direction of plane waves is generally perpendicular to the isophase plane, the designed metasurface produces an isophase plane with a certain slope at the transmissive and reflective ends to make outgoing light emerge at an angle, which in turn realizes the metasurface design's deflection beam-splitting function for the incident light on the positive \(y\)-axis. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Radius (\(\upmu\)m)** & 0.27 & 0.33 & 0.36 & 0.37 & 0.38 \\ \hline
**Phase** & 0 & 0.50\(\uppi\) & 1.16\(\uppi\) & 1.48\(\uppi\) & 1.63\(\uppi\) \\ \hline
**T(\%)** & 93.74 & 91.12 & 94.97 & 99.75 & 0.18 \\ \hline \end{tabular}
\end{table} 
Table 1: The transmittance and additional phase for the various radii. Figure 2: **(a)** The phase (red line) and transmittance curves (blue line) of outgoing light at 1.55 \(\upmu\)m wavelength when the nanocolumn radius changes from 0.15 \(\upmu\)m to 0.45 \(\upmu\)m. The radius dimension points of the selected metasurface unit cell structure are marked in green. **(b)** The transmittance curves corresponding to different distances of nanocolumns. In order to show the more intuitive light emission conditions at both ends of the metasurface under x and y-line polarization light incidence, we obtained the double-ended light field intensity distribution as shown in Figure 4. We can see the more obvious double-ended polarized light emission along the positive \(y\)-axis and located on the same side of the optical normal. To demonstrate the polarization-maintaining performance and the power variation of the BS, the polarization direction of the incident beam was changed from 0 degrees (x-line polarized light) to 90 degrees (y-line polarized light) in a step of 15 degrees. Figure 4: The normalized intensity of the Y\(-\)Z plane at the reflective and transmissive ends of the metasurface beam splitter under the incidence of x-polarized light at 1.55 μm wavelength demonstrates the deflection of the outgoing light. (**a**) The intensity of the Y\(-\)Z plane at the reflective end of the metasurface beam splitter under the incoming x-polarized light of 1.55 μm wavelength. Figure 3: The Y\(-\)Z plane phase diagrams of the reflective and transmissive ends of the metasurface beam splitter under two types of line-polarized incident light at 1.55 μm wavelength reflect the isophase plane of the outgoing light waves, 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. (**a**) The isophase plane of the reflective end under the incident x-line polarized light. (**b**) The isophase plane of the transmissive end under the incident x-line polarized light. (**c**) The isophase plane of the reflective end under the incident y-line polarized light. (**d**) The isophase plane of the transmissive end under the incident y-line polarized light. (**b**) The intensity of the Y\(-\)Z plane at the transmissive end of the metasurface beam splitter under the incoming x-polarized light of 1.55 \(\upmu\)m wavelength. (**c**) The intensity of the Y\(-\)Z plane at the reflective end of the metasurface beam splitter under the incoming y-polarized light of 1.55 \(\upmu\)m wavelength.