A Hybrid Achromatic Plasmonic Metalens

Abstract Meta‐lenses can break the performance limits of traditional bulky lenses and are essential for the development of advanced meta‐devices and systems. However, chromatic dispersion represents a significant challenge in the metalenses design for their widespread applications. Previous studies on broadband achromatic metalenses are mostly based on all‐dielectric metasurfaces, and very little efforts are devoted to the design of achromatic plasmonic metalenses. Herein, an ultra‐thin broadband hybrid achromatic plasmonic metalens with only 0.08 λ 0 thickness (λ 0 is the central wavelength) is designed, presented, and characterized in low spectrums. Compared to previous broadband plasmonic metalenses with single positive or negative chromatic dispersion, the aberration of hybrid plasmonic metalens is significantly reduced by an order of magnitude. High average numerical aperture exceeding 0.8 is achieved in the simulations across the considered broad bandwidth. Besides, a high average focusing efficiency of 60% (the maximum is nearly 80%) is also measured in the experiments. These excellent focusing performances can break the tradeoffs of current achromatic metalenses. More importantly, the presented hybrid plasmonic metalens provides a novel and general concept to develop broadband achromatic metalenses with a fully planar and low‐profile device footprint.