Integrated Resonant Unit of Metasurfaces for Broadband Efficiency and Phase Manipulation

Integrated-resonant units (IRUs), incorporated with multiple resonators into one building block or one resonator with multiple modes, show a great capacity for achieving controllable smooth and linear phase dispersion as well as amplitude manipulation over a continuous and broad bandwidth. Based on an IRU library designed in the wavelength range of 400 to 667 nm, three achromatic deflectors showing constant steering angles of 9.5°, 19°, and 28°, respectively, are numerically validated. Achromatic metalenses with various numerical aperture (NA) values are further experimentally demonstrated, displaying an unvaried focal length throughout the bandwidth of 420–650 nm (≈50% bandwidth to the central wavelength). The focusing efficiency of the achromatic metalens with NA = 0.124 achieves 26.31%, 19.71%, and 20.37%, respectively, at wavelengths of 420, 550, and 650 nm. In addition, a multi-nanorod IRU design is numerically optimized to achieve above 50% conversion efficiency from visible to near-infrared (400–1400 nm). Such IRU design is then employed to construct a versatile polarization convertor, generating six different polarization states simultaneously upon one linear-polarized illumination. The IRU approach with broadband control of amplitude and phase response provides an unprecedented platform in realizing multifunctional full-color metadevices.