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Extreme-angle broadband metamaterial lens

Nature Materials volume 9, pages 129–132 (2010)Cite this article

Abstract

For centuries, the conventional approach to lens design has been to grind the surfaces of a uniform material in such a manner as to sculpt the paths that rays of light follow as they transit through the interfaces. Refractive lenses formed by this procedure of bending the surfaces can be of extremely high quality, but are nevertheless limited by geometrical and wave aberrations that are inherent to the manner in which light refracts at the interface between two materials. Conceptually, a more natural—but usually less convenient—approach to lens design would be to vary the refractive index throughout an entire volume of space. In this manner, far greater control can be achieved over the ray trajectories. Here, we demonstrate how powerful emerging techniques in the field of transformation optics can be used to harness the flexibility of gradient index materials for imaging applications. In particular we design and experimentally demonstrate a lens that is broadband (more than a full decade bandwidth), has a field-of-view approaching 180∘ and zero f-number. Measurements on a metamaterial implementation of the lens illustrate the practicality of transformation optics to achieve a new class of optical devices.

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Figure 1: Ray tracing results for spherical and flattened Luneburg lenses.
Figure 2: The transformation used to produce the flattened Luneburg lens.
Figure 3: Lens design and fabrication.
Figure 4: Experimental field maps of the flattened lens.

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Acknowledgements

This work was partially supported through a Multiple University Research Initiative, sponsored by the Army Research Office (Contract No. W911NF-09-1-0539). The authors are grateful to J. Mock for helpful discussions and suggestions.

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Authors and Affiliations

  1. Department of Electrical and Computer Engineering, Center for Metamaterials and Integrated Plasmonics, Duke University, Durham, North Carolina 27708, Box 90291, USA

    Nathan Kundtz & David R. Smith

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  1. Nathan Kundtz
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  2. David R. Smith
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Contributions

N.K. and D.R.S. jointly conceived the strategy of leveraging QCTO for the lens flattening procedure. N.K. conceived of using the inverse transform, implemented a relaxation method to carry out the transform, designed the metamaterial lens and characterized the lens though simulations, ray-tracing and experiment. D.R.S. supervised the design and execution of the experiments. The manuscript was prepared by N.K. in collaboration with D.R.S.

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Correspondence to Nathan Kundtz.

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The authors declare no competing financial interests.

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Kundtz, N., Smith, D. Extreme-angle broadband metamaterial lens. Nature Mater 9, 129–132 (2010). https://doi.org/10.1038/nmat2610

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