Metasurfaces have revolutionized the definition of compact optics. Using subwavelength periodic structures ofnanostructured dielectrics, the refractive index and absorption properties of metasurfaces – which are 2D metamaterials –can manipulate light to a degree not possible with conventional bulk glasses and crystals. The phase, polarization, spin(for circularly polarized light), amplitude and wavelength of light can all be manipulated and crafted to user-specifiedvalues to mimic the action of a lens, which we refer to as a metalens (ML). MLs have four major advantages overtraditional refractive lenses – superior resolution, lighter weight, miniaturization and cost. Many metasurfaces withuseful functionalities have been proposed in recent years, yet although novel in their approach have few real-worldapplications. One such market is the use within infrared laser systems, such as laser designators. In this work, wedemonstrate metasurface lenses working at a wavelength of λ = 1064 nm, with aperture d = 1 mm and four different Fnumbers(focal length f = 0.5, 1, 2 and 5 mm). The lenses are composed of 700nm high a-Si pillars – ranging from 70-360 nm diameter – which are fabricated using electron beam lithography (EBL) and reactive ion etching processes, ontop of a fused silica substrate. Such lenses are shown to have diffraction-limited performance, with focal spot-sizeagreeing with theoretical values of λ‧f/d. Furthermore, we have designed large area lenses with aperture d = 10 mm,where the number of pillars per lens exceeds 550 million. By using an efficient Python script, we are able to producethese 100 mm~2 samples with just 14 hours of EBL writing time.
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