Metalenses, planar lenses realized by placing subwavelength nanostructures that locally impart lenslike phase shifts to the incident light, are promising as a replacement for refractive optics for their ultrathin, lightweight, and tailorable characteristics, especially for applications where payload is of significant importance. However, the requirement of fabricating up to billions of subwavelength structures for centimeter-scale metalenses can constrain size-scalability and mass-production for large lenses. In this Letter, we demonstrate a centimeter-scale, all-glass metalens capable of focusing and imaging at visible wavelength, using deep-ultraviolet (DUV) projection stepper lithography. Here, we show size-scalability and potential for mass-production by fabricating 45 metalenses of 1 cm diameter on a 4 in. fused-silica wafer. The lenses show diffraction-limited focusing behavior for any homogeneously polarized incidence at visible wavelengths. The metalens’ performance is quantified by the Strehl ratio and the modulation transfer function (MTF), which are then compared with commercial refractive spherical and aspherical singlet lenses of similar size and focal length. We further explore the imaging capabilities of our metalens using a color-pixel sCMOS camera and scanning-imaging techniques, demonstrating potential applications for virtual reality (VR) devices or biological imaging techniques.

Existing methods of correcting for chromatic aberrations in optical systems are limited to two approaches: varying the material dispersion in refractive lenses or incorporating grating dispersion via diffractive optical elements. Recently, single-layer broadband achromatic metasurface lenses have been demonstrated but are limited to diameters on the order of 100 μm due to the large required group delays. Here, we circumvent this limitation and design a metacorrector by combining a tunable phase and artificial dispersion to correct spherical and chromatic aberrations in a large spherical plano-convex lens. The tunability results from a variation in light confinement in sub-wavelength waveguides by locally tailoring the effective refractive index. The effectiveness of this approach is further validated by designing a metacorrector, which greatly increases the bandwidth of a state-of-the-art immersion objective (composed of 14 lenses and 7 types of glasses) from violet to near-infrared wavelengths. This concept of hybrid metasurfacerefractive optics combines the advantages of both technologies in terms of size, scalability, complexity, and functionality.

The key components of a spectrometer are a dispersive element, such as a grating, followed by a focusing lens. These are usually arranged in a Czerny-Turner configuration. [7] However, different wavelengths of incident light are focused along a curved surface as opposed to a planar one; as a result the focal spot broadens and becomes aberrated due to astigmatism and field curvature. [7] These factors result in a tradeoff between the spectral resolution, which is related to the size and quality of the focal spot, and the spectral range of the spectrometer.Conventional methods to overcome this challenge involve additional optical components (e.g., multiple lenses) or precisely machined parts to correct for these aberrations, such as wedge-shaped cylindrical lenses, [8] toroidal gratings, [9] and freeform elements. [10] These are typically fabricated from aspheric blanks and introduce a significant overhead in terms of overall device cost and complexity. This also poses a significant challenge for truly compact, low-cost, handheld aberration-corrected spectrometers.Recently, metasurfaces comprising of subwavelength scale nanostructures have received much attention from the research community. [11] They allow for exquisite control over the output wavefront of light, [12][13][14][15] and have been used to demonstrate ultracompact analogs of numerous optical components, such as lenses, [16][17][18] holograms, [19][20][21] and polarimeters. [22][23][24] An important advantage of metasurfaces is their ability to integrate multiple functionalities within a single planar device, thereby greatly reducing bulk and system complexity. For example, in an earlier work, [25] we demonstrated off-axis focusing metalenses capable of simultaneously focusing and dispersing light: they thus integrate the functionality of both the grating and the focusing lens in a single optical component. Additionally, by engineering the off-axis focusing angle very large dispersions can be obtained; [26] this allows one to achieve a miniature spectrometer with subnanometer resolution with a working distance of only a few centimeters from the lens to the detector. This distance is not fundamentally limited in any way; it is dependent on the desired specifications of the metalens, and in principle could even be much smaller, enabling monolithic integration with detectors.However, these off-axis focusing metalenses face the same challenges as their refractive and diffractive counterparts [27][28][29][30] The spectral resolution and range of conventional spectrometers are typically limited by optical aberrations of their focusing elements, mainly due to chromatically induced astigmatism and an intrinsically curved focal plane. Traditional approaches to overcome this challenge require additional optical components which introduce significant bulk and design complexity to the system and prevent easy integration with portable devices. Here a single planar off-axis focusing metalens consisting of subwavelength TiO 2 nanofins whose focal spots lie along a pla...