Metasurface-Based Ultrathin Beam Splitter with Variable Split Angle and Power Distribution

Metasurfaces are artificial electromagnetic surfaces that consist of subwavelength scatterers in an array configuration, exhibiting exceptional abilities to manipulate electromagnetic waves. Based on the metasurface concept, a novel beam splitter for a single-frequency same-polarization light is proposed in the visible spectrum. Using metal dielectric metal (MDM) scattering unit cells, an array of the circular gold nanocylinders with two different diameters is designed and fabricated on the surface which introduces phase discontinuity on the scattering wavefronts. At 240 nm thick, the flat beam splitter can efficiently reflect an incident wave toward two predesigned directions. More importantly, the split angle and power distribution between these two beams can be readily controlled by setting a proper incident angle. Compared to conventional bulky optical components, the ability of this metasurface-based beam splitter would be very desirable in integrated optical systems.