Design of a dielectric ultrathin near-infrared metalens based on electromagnetically induced transparency

A transmissive metasurface lens thinner than a wavelength promises a potential way to replace conventional bulky components for wavefront and polarization control of incident light. Here we propose a novel approach for an ultrathin metasurface lens at the working wavelength of 1550 nm composed of silicon cuboids on the silica substrate. Taking advantage of the 'slow-light' effect of the electromagnetically induced transparency (EIT) phenomena, the thickness of the proposed transmissive metalens has been reduced to 130 nm (similar to 1/12 lambda(0)), and it can focus incident light to a near diffraction-limited spot. The focusing efficiency of the ultrathin metalens is about 2 times larger than its peer without EIT effect. One key advantage of this metalens design is the reduction of the aspect ratio down to about 1, making this approach significantly degrade the difficulty of metalens manufacturing.