Multifunctional Metamirror: Polarization Splitting and Focusing

Metasurfaces are paving the way to improve traditional optical components by integrating multiple functionalities into one optically flat metasurface design. We demonstrate the implementation of a multifunctional gap surface plasmon-based metasurface that in reflection mode splits orthogonal linear light polarizations and focuses them into different focal spots. The fabricated configuration consists of 50 nm thick gold nanobricks with different lateral dimensions organized in an array of 240 nm x 240 nm unit cells on top of a 50 nm thick silicon dioxide layer, which is deposited on an optically thick reflecting gold substrate. Our device features high efficiency (up to similar to 65%) and polarization extinction ratio (up to similar to 30 dB), exhibiting broadband response in the near-infrared band (750-950 nm wavelength) with the focal length dependent on the wavelength of the incident light. The proposed optical component can be forthrightly integrated into photonic circuits or fiber-optic devices.