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On-chip zero-index metamaterials


Metamaterials with a refractive index of zero exhibit physical properties such as infinite phase velocity and wavelength. However, there is no way to implement these materials on a photonic chip, restricting the investigation and application of zero-index phenomena to simple shapes and small scales. We designed and fabricated an on-chip integrated metamaterial with a refractive index of zero in the optical regime. Light refracts perpendicular to the facets of a prism made of this metamaterial, directly demonstrating that the index of refraction is zero. The metamaterial consists of low-aspect-ratio silicon pillar arrays embedded in a polymer matrix and clad by gold films. This structure can be fabricated using standard planar processes over a large area in arbitrary shapes and can efficiently couple to photonic integrated circuits and other optical elements. This novel on-chip metamaterial platform opens the door to exploring the physics of zero index and its applications in integrated optics.

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Figure 1: Metamaterial design and structure fabricated to demonstrate in-plane zero index.
Figure 2: Optical properties of the zero-index metamaterial.
Figure 3: Simulation and experimental results.


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The authors thank X.Q. Huang, Y. Wu, C. Simovski, C.C. Evans and Y.M. Yang for discussions, N. Liu for assistance with finite-difference time-domain simulations, Q.M. Quan for assistance with the measurements, M. Kats for providing the measured complex index of gold and K. Phillips for guidance on the preparation of the figures. The research described in this Article was supported by the National Science Foundation under contract DMR-1360889, the Air Force Office of Scientific Research under contract FA9550-14-1-0389, the Natural Sciences and Engineering Research Council of Canada and the Harvard Quantum Optics Center.

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Y.L. conceived the basic idea for this work. Y.L., P.M. and D.V. carried out the FDTD simulations. S.K., O.R. and M.Y. carried out the FEM simulations. O.R. designed the optical waveguides. S.K. performed the fabrication. S.K., O.R. and D.V. carried out the measurements. P.M. analysed the experimental results. M.L. and E.M. supervised the research and the development of the manuscript. Y.L. wrote the first draft of the manuscript, and all authors subsequently took part in the revision process and approved the final copy of the manuscript.

Corresponding authors

Correspondence to Marko Lončar or Eric Mazur.

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The authors declare no competing financial interests.

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Li, Y., Kita, S., Muñoz, P. et al. On-chip zero-index metamaterials. Nature Photon 9, 738–742 (2015).

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