Broadband Achromatic Metasurface-Refractive Optics

Abstract

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.

Octopi: Open configurable high-throughput imaging platform for infectious disease diagnosis in the field

“…The compactness and light weight makes it possible to mount the lens on a voice coil actuator (widely used in cellphone cameras and blu-ray players), eliminating the need for linear stage, which results in reduction in cost and form factor. Metasurfaces or phase masks may also be incorporated into the optical train for aberration correction [62] and for enhanced 3D imaging capability through point spread function engineering [63, 64, 65]. While all images in this report are taken with Pi cameras, CMOS cameras that are low-cost and compact but rival the performance of sCMOS and EMCCD can be used for more demanding applications [66, 67, 68, 69].…”

Ultrathin Single Layer Metasurfaces with Ultra‐Wideband Operation for Both Transmission and Reflection

“…On the other hand, transmissive metasurfaces presented in literature suffers due to limited bandwidth as a result of rapid phase variation away from the design frequency due to dispersion. In visible spectra, many techniques are available to compensate for additional phase delay, such as hybrid metasurfaces,25 super oscillatory lens,26 and catenary optics,27 to name a few. These techniques are based on all‐dielectric devices and are not commonly utilized in microwave spectrum due to fabrication issues and large thickness rendering them incompatible with the integrated devices.…”

Progresses in the practical metasurface for holography and lens

“…Typically, in the case of achromatic metalens in the visible band, which is considered to be the most actively used, it is difficult to realize a meta-atom that can satisfy both long diameter and high numerical aperture. In this regard, the dispersion-engineered metasurface is used as a dispersion corrector in addition to the refractive optics system [164]. The result is desirable in performance, but not sufficiently attractive in compactness.…”