Polarization-independent broadband achromatic metalens in the mid-infrared (3-5 μm) region

With superior capabilities for light manipulation and wavefront shaping, the metasurface recently has caught growing attention. However, the presence of chromatic aberration hinders metasurfaces, especially metalenses, from wider applications. Here, we design a polarization-independent broadband achromatic focusing metalens in the mid-infrared region, which covers continuous bands in 3-5 μm. Numerical simulation shows that different wavelengths can be focused to the same plane with a nearly diffraction-limited resolution, and can achieve an average focusing efficiency of nearly 70% in the whole bandwidth. We expect that our approach can underpin the development of integrated and mid-infrared imaging and detection.