Design framework for polarization-insensitive multifunctional achromatic metalenses

Jacob T Heiden,Min Seok Jang

doi:10.1515/nanoph-2021-0638

Jacob T Heiden, Min Seok Jang

Open Access

https://doi.org/10.1515/nanoph-2021-0638

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Abstract

Abstract Controlling the wavefront of light, especially on a subwavelength scale, is pivotal in modern optics. Metasurfaces present a unique platform for realizing flat lenses, called metalenses, with thicknesses on the order of the wavelength. Despite substantial effort, however, suppressing the chromatic aberrations over large operational bandwidths of metalenses still remains a challenge. Here, we develop a systematic design method enabling a simultaneous, polarization-insensitive control of the phase and the group delay of a light beam based on libraries of transmission-mode dielectric meta-elements. Mid-infrared achromatic metalenses are designed and theoretically analyzed to have diffraction-limited focal spots with vanishing chromatic aberrations in the operating wavelength range of 6–8.5 μm, while maintaining high focusing efficiencies of 41% on average. The proposed methodology, which can be used as a general design rule for all spectra, also provides a versatile design scheme for ultrashort pulse focusing and achromatic vortex-beam generation (orbital angular momentum), representing a major advance toward practical implementations of functional metalenses.

Highlights

Controlling light propagation through media is essential in light-energy-delivery and imaging systems
Metasurfaces present a unique platform for realizing flat lenses, called metalenses, with thicknesses on the order of the wavelength
Metalenses have especially attracted significant interest due to their applicability in compact imaging systems for both consumer and industry products encompassing cameras, microscopy, and lithography. Such metalenses will generally suffer from considerable chromatic aberration, which can be attributed to two separate factors: resonant or guided light confinement, and periodic lattice dispersion

Summary

Introduction

Controlling light propagation through media is essential in light-energy-delivery and imaging systems. Metasurfaces composed of subwavelength-spaced structures at a planar surface provide unprecedented control over the properties of the electromagnetic field, including amplitude, phase, and polarization, and are attracting increasing attention [2,3,4] This unique approach, for tailoring the optical response, has been utilized for numerous applications in the infrared and visible spectrums, including holograms [5,6,7,8,9], polarimeters [10,11,12], polarization elements [13,14,15,16], and flat lenses (metalenses) [9, 17,18,19,20,21,22]. In the MIR, achromatic metalenses could be well suited for integration with other nano-optical components for molecular sensing or bioimaging [35, 44]

Results and discussion

Conclusions

Methods