Light defies geometry in near-zero-index media

DIPC Seminars

Iñigo Liberal, Universidad Publica de Navarra
Donostia International Physics Center
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Light defies geometry in near-zero-index media Continuous media and metamaterials with a near-zero refractive index (NZI media) provide alternative pathways for the control and manipulation of light- matter interactions. The exotic behavior of NZI media is rooted in the fact that the wavelength gets effectively stretched as the refractive index vanishes. This allows for pathological solutions to the wave equation, including spatially static field distributions which nevertheless dynamically oscillate in time. This paradoxical behavior gives access to a regime of qualitatively different wave dynamics, where the importance of the geometry is lessened, and certain observables are invariant with respect to geometrical deformations, even including changes in the topology of the system. In this talk, I’ll review and discuss some of the geometry-invariant phenomena related to near-zero-index media. Examples will include: (i) transmission (tunneling) of waves through deformed waveguides. (ii) Unconventional resonators supporting modes whose eigenfrequency is independent of the geometry of their external boundary. (iii) Violation of effective medium theory geometrical restrictions, enabling, for example, single unit- cell metamaterials. (iv) Existence of bound states in open 3D compact resonators with arbitrarily shaped boundaries. Different technological applications and implementations of these concepts will be discussed. **References** I. Liberal and N. Engheta, “Near-zero refractive index photonics,” Nat. Photonics, vol. 11, no. 3, pp. 149–158, 2017. I. Liberal, A. M. Mahmoud, and N. Engheta, “Geometry-Invariant Resonant Cavities,” Nat. Commun., vol. 7, p. 10989, 2016. I. Liberal, A. M. Mahmoud, Y. Li, B. Edwards, and N. Engheta, “Photonic doping of epsilon-near-zero media,” Science, vol. 355, pp. 1058–1062, 2017. I. Liberal and N. Engheta, “Zero-index structures as an alternative platform for quantum optics,” _Proc._ _Natl. Acad. Sci. USA_ , vol. 114, no. 5, pp. 822–827, 2017. I. Liberal and N. Engheta, “Nonradiating and radiating modes excited by quantum emitters in open epsilon-near-zero cavities,” _Sci. Adv._ , vol. 2, no. 10, p. e1600987, 2016.