Nonimaging metaoptics

Abstract

So far, metalenses have only been studied in imaging optics, where a point from the object space is mapped to a corresponding point in the image space. Here we explore metalenses and metamirrors for dealing with the optimal transfer of light energy. Owing to its compactness and high design flexibility, metasurface-based flat optics may open new opportunities in the nonimaging field, which deals with light concentration and illumination. The building blocks of metalenses are subwavelength-spaced scatterers. By suitably adjusting their shape, size, position, and orientation, one can control the light spatial distribution, as is desired in nonimaging problems. In this Letter, we introduce nonimaging metaoptics, review its basics, and briefly explore three cases: the compound-metasurface concentrator [analogous to the compound parabolic concentrator (CPC)], the total internal reflection (TIR) metalens (analogous to the TIR lens), and a simple condensing metalens.

Optics of the metalens

“…where, R 1 and R 2 are the first and second radii of curvature of the lens, k 0 is the vacuum wave number, Φ 0 is the phase shift introduced on the optical axis, and n is the refractive index of the thin lens. Here we must note that, as is well-known, a thin refractive lens satisfies the lens equation given by equation (12). We can see that equation ( 13) contains the well-known lens makers' equation:…”

“…If the phase profile function Φ is constant dΦ/dr = 0, and equation ( 1) becomes the well-known Snell law. On the other hand, the mathematical expressions for more general cases, like those for raytracing in a metalens may be found in [12,13]. Refraction of a wave at a metasurface, and Huygens's construction for deriving the law of refraction.…”

Multilayer dielectric reflective metalens without metallic mirror

“…The ultra-thin nature of metalens paves the way for new developments. For example, in the development of compact and high-performance systems with a wide range of applications including imaging, spectroscopy, lithography, nonimaging optics, among others [3][4][5][6]. Metalenses can be designed to operate in both transmission and reflection modes, each mode presenting unique advantages and applications [7][8][9].…”

An LED metalens for uniform illumination

“…Metalenses are finding new applications as nonimaging metalenses [5,6]. Therefore, here we analyze a simple case of metalens beam shaping for uniform illumination.…”