Abstract

Abstract We design and fabricate ultra-broadband achromatic metalenses operating from the visible into the short-wave infrared, 450–1700 nm, with diffraction-limited performance. A hybrid 3D architecture, which combines nanoholes with a phase plate, allows realization in low refractive index materials. As a result, two-photon lithography can be used for prototyping while molding can be used for mass production. Experimentally, a 0.27 numerical aperture (NA) metalens exhibits 60% average focusing efficiency and 6% maximum focal length error over the entire bandwidth. In addition, a 200 μm diameter, 0.04 NA metalens was used to demonstrate achromatic imaging over the same broad spectral range. These results show that 3D metalens architectures yield excellent performance even using low-refractive index materials, and that two-photon lithography can produce metalenses operating at visible wavelengths.

Highlights

  • Metalenses, lenses composed of quasi-periodic subwavelength structures, have received a great deal of attention due to their compact size, light weight, efficient wavefront shaping, and polarization conversion properties [1,2,3,4,5,6]

  • A 200 μm diameter, 0.04 numerical aperture (NA) metalens was used to demonstrate achromatic imaging over the same broad spectral range. These results show that 3D metalens architectures yield excellent performance even using lowrefractive index materials, and that two-photon lithography can produce metalenses operating at visible wavelengths

  • Diffractive achromatic doublet design by recursive raytracing has been proposed and experimentally verified by Farn et al [27, 28]. We recently adapted this design approach to achromatic metalenses in the near infrared region (1000–1800 nn) [25]. We extend this approach to create a visible to short-wave infrared achromatic metalens and identify a geometry that is amenable to 3D printing via two-photon lithography

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Summary

Introduction

Metalenses, lenses composed of quasi-periodic subwavelength structures, have received a great deal of attention due to their compact size, light weight, efficient wavefront shaping, and polarization conversion properties [1,2,3,4,5,6]. We present an achromatic metalens operating with diffraction-limited performance over almost two octaves from 450 to 1700 nm. This spectral range is well matched to visible-to-shortwave infrared image sensors that are becoming available. We used a variable height nanopillar metasurfaces created with two-photon lithography [25, 26] These nanopillar arrays lose structural integrity when the feature size is reduced for operation at visible wavelengths. F. Balli et al.: 3D achromatic metalens not obvious that such a system has sufficient resolution to produce metalenses operating at visible wavelengths. The metalens designs lack re-entrant features; they could be molded for high volume production

Theory and structure
Experimental results

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