High efficiency independent modulation at dual-wavelength based on Pancharatnam-Berry and propagation phases

Metasurfaces capable of controlling multiple wavelengths independently have attracted broad interests these years due to their significance in multi -channel information processing applications. Previous solving strategies include spatial multiplexing or extensive searching for appropriate structures, both of which have their own disadvantageous, such as low efficiency, large computer resource requirement, or time consumption. In this paper, by combining the Pancharatnam-Berry (PB) phase and propagation phase, we propose a strategy to simplify the design complexity in a dual -wavelength metasurface system, in which two simple rectangular -shaped dielectric pillars ( T 1 and T 2 ) with different aspect ratios are chosen as basic structures and crossed at the geometric center to achieve manipulation. The larger pillar T 2 controls the longer wavelength through the PB phase while the smaller T 1 acts as a perturbation to T 2 . The crossed T 1 & T 2 is studied as a whole to tune the short wavelength. The investigations by the multipole expansion method reveal that the polarization conversion ratio of the meta -atoms is dependent on the interference of the formed multipoles. To validate the proposed strategy, a dual -wavelength achromatic metalens and a wavelength -multiplexed holographic metasurface operating at the infrared thermal imaging band are designed. Our design strategy can find widespread applications in metasurfaces where multiple objectives are required to be realized. (c) 2024 Optica Publishing Group