Broadband metasurface aberration correctors for hybrid meta/refractive MWIR lenses

A method for designing multi-metasurface layouts for optical aberration correction is presented. All-dielectric metasurfaces are combined with conventional refractive optics to form a hybrid lens. The optical power of a hybrid lens is primarily provided by refractive optics, and metasurfaces are optimized to control optical aberrations. This approach greatly reduces the magnitude of phase gradient required for a largescale metasurface and hence its diffraction loss. An inverse design technique is incorporated to optimize all physical parameters on a metasurface to minimize image spots across all sampling field angles and wavelengths. This approach is put to test by designing a hybrid lens composed of a midwave infrared refractive lens followed by a pair of metasurfaces. Moreover, we demonstrate the working bandwidth of the hybrid lens can be further extended by reducing phase dispersion introduced by a metasurface using holey meta-atoms instead of pillar meta-atoms.