Wide-field large-angle beam splitters based on polarization-insensitive coding metasurfaces.

Metasurfaces have been used to make various optical devices such as beam splitters because of their excellent capability to control light. The most recent work on metasurface beam splitters focused on realizing one-dimensional beam splitting. Based on generalized Snell's law, we designed the beam splitters using a coding strategy by phase gradient metasurfaces, which can divide vertically incident light into two-dimensional space. Meanwhile, the beam splitters are polarization-insensitive because highly rotationally symmetric nanorods are used as structure units. Using different code groups, especially applying 0 and binary phases, the proposed beam splitters have various functions such as beam deflection, two-beam splitting, and multi-beam splitting. The flexible design of the coding maps allows the light transmission to cover a full-view field. The maximum splitting angles in two-beam and multi-beam splitters are 35.7° and 28.3°, respectively. All the designed beam splitters have a power efficiency of over 80%. The beam splitters have the advantages of small size, easy integration, large beam splitting angle, wide beam splitting area, and high efficiency. They could be applied to many optical systems, such as multiplexers and interferometers in integrated optical circuits.