Giant broadband refraction in the visible in a ferroelectric perovskite


In principle, materials with a broadband giant index of refraction (n > 10) overcome chromatic aberration and shrink the diffraction limit down to the nanoscale, allowing new opportunities for nanoscopic imaging1. They also open alternative avenues for the management of light to improve the performance of photovoltaic cells2. Recent advances have demonstrated the feasibility of a giant refractive index in metamaterials at microwave and terahertz frequencies3,4, but the highest reported broadband index of refraction in the visible is n < 5 (ref. 5). Here, we report a ferroelectric perovskite with an index of refraction of n > 26 across the entire visible spectrum and demonstrate its behaviour using white-light and laser refraction and diffraction experiments. The sample, a solid-solution K0.997Ta0.64Nb0.36:Li0.003 (KTN:Li) perovskite6,7,8,9,10,11,12, has a naturally occurring room-temperature phase that propagates visible light along its normal axis without significant diffraction or chromatic dispersion, irrespective of beam size, intensity and angle of incidence.

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Fig. 1: Giant refraction.
Fig. 2: White-light experiments.
Fig. 3: Monochromatic experiments and the physical origin of GR.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


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The authors acknowledge funding from grants Sapienza 2016/2017 and Lazio Innova 2017. A.J.A. acknowledges the support of the Peter Brojde Center for Innovative Engineering.

Author information




F.D.M. and E.D. conceived and designed the experiments. F.D.M., L.F., M.F., D.P., P.D.P. and E.D. carried out the investigation and the experiments. A.J.A. designed and grew the crystal samples. All authors discussed the results and wrote the paper.

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Correspondence to F. Di Mei.

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Supplementary Information

This file contains additional photographs and analysis.

Supplementary Video 1

A sequence of videos of the giant refraction effect.

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Di Mei, F., Falsi, L., Flammini, M. et al. Giant broadband refraction in the visible in a ferroelectric perovskite. Nature Photon 12, 734–738 (2018).

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