Integrated resonant units of metasurface for broadband efficiency and phase modulation

The beauty of metasurfaces lies on their capability for controlling the amplitude, phase, and polarization response with subwavelength resolution via spatially-varying nano-scatterers. With the incorporation of multiple elements or multiple resonances of nano-resonators into metasurfaces, these integrated-resonant units (IRUs) provide additional degree of freedom to manipulate the multispectral optical property of scattering light over a continuous and broad bandwidth, which is especially essential for eliminating the chromatic effect that requires smooth and linear phase dispersion. Here, we demonstrated three achromatic meta-lens based on IRUs designs to show constant focal length in the range of 400 to 650 nm. In addition, a broadband versatile polarization generator operating in 400 nm to 1300 nm was demonstrated by using multi-nanorod IRUs as building blocks. The working efficiency of multi-nanorod design is enhanced above 10 times in the near infrared range compared to the optimization case of single nanorod design, demonstrating the capability of IRUs in achieving high conversion efficiency over a broad wavelength range.