Fundamental limits and design principles of doublet metalenses

Augusto Martins,Emiliano R Martins,Juntao Li,Thomas F Krauss,Ben-Hur V Borges

doi:10.1515/nanoph-2021-0770

Augusto Martins, Emiliano R Martins + Show 3 more

Open Access

https://doi.org/10.1515/nanoph-2021-0770

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Abstract

Abstract Metalenses are nanostructured surfaces with great potential for delivering miniaturized and integrated optical systems. A key property of metalenses is that, by using a double layer configuration, or doublet, they can achieve both diffraction-limited resolution and wide field-of-view imaging. The physical operation and limitations of such doublet systems, however, are still not fully understood, and designs are still based on numerical optimization of the phase profiles. Here, we show the fundamental limits of doublet systems and provide a universal design strategy without any need to resort to numerical optimization. We find an analytical relationship between the focal length and the spacer thickness; we identify the physical principles underlying the limitations on performance and obtain a universal dependence of the field of view as a function of resolution (numerical aperture). Our results will allow researchers to appreciate the regimes of resolution and field of view that are accessible for specific applications, to identify the conditions for optimum performance (such as required spacer thickness), and to conveniently design doublets without needing to resort to numerical optimizations.

Highlights

Metalenses are an emerging technology that holds great promise to deliver miniaturized and lightweight optical systems at a low cost [1,2,3,4]
We find an analytical relationship between the focal length and the spacer thickness; we identify the physical principles underlying the limitations on performance and obtain a universal dependence of the field of view as a function of resolution
We have examined the physical principles underlying the operation of doublet metalenses

Summary

Introduction

Metalenses are an emerging technology that holds great promise to deliver miniaturized and lightweight optical systems at a low cost [1,2,3,4]. A major advantage of metalenses is their versatility in modulating an optical beam by appropriately engineering their constituent meta-atoms, especially for the generation of arbitrary phase profiles Such versatility is explored in a number of applications, such as diffraction-limited focusing [5,6,7,8,9], achromatic focusing [10,11,12,13,14,15,16,17,18,19], Stokes cameras [20], and endoscopic optical systems [21, 22], to mention but a few. It is clear from fundamental principles that the only way to improve the FOV of diffraction-limited metalenses is through a double-layer configuration, or doublet [4] Such a requirement is an instance of the well-known principle of optical systems that the simultaneous correction of off-axis and spherical aberrations requires more than one surface.

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