Multiwavelength polarization insensitive lenses based on dielectric   metasurfaces with meta-molecules
  Metasurfaces are nano-structured devices composed of arrays of subwavelength scatterers (or meta-atoms) that manipulate the wavefront, polarization, or intensity of light. Like other diffractive optical devices, metasurfaces suffer from significant chromatic aberrations that limit their bandwidth. Here, we present a method for designing multiwavelength metasurfaces using unit cells with multiple meta-atoms, or meta-molecules. Transmissive lenses with efficiencies as high as 72% and numerical apertures as high as 0.46 simultaneously operating at 915 nm and 1550 nm are demonstrated. With proper scaling, these devices can be used in applications where operation at distinct known wavelengths is required, like various fluorescence microscopy techniques. 
Ehsan Arbabi, Amir Arbabi, Seyedeh Mahsa Kamali, Yu Horie, Andrei   Faraon
physics.optics