Abstract-Realization of an all-dielectric zero-index optical metamaterial

 

                                                     a, IFCs of air and a low-index metamaterial, illustrating angularly
                                                     selective transmission due to conservation of the wave vector parallel
                                                     to the surface. b, Simulated angle- and wavelength-dependent transmittance
                                                     of the fabricated struture.

Parikshit Moitra,^{1, 5}Yuanmu Yang,^{1, 5}Zachary Anderson,² Ivan I. Kravchenko,³Dayrl P. Briggs³ Jason Valentine⁴
http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2013.214.html

Metamaterials offer unprecedented flexibility for manipulating the optical properties of matter, including the ability to access negative index^{1, 2, 3, 4}, ultrahigh index⁵ and chiral optical properties^{6, 7, 8}. Recently, metamaterials with near-zero refractive index have attracted much attention^{9, 10, 11, 12, 13}. Light inside such materials experiences no spatial phase change and extremely large phase velocity, properties that can be applied for realizing directional emission^{14, 15, 16}, tunnelling waveguides¹⁷, large-area single-mode devices¹⁸ and electromagnetic cloaks¹⁹. However, at optical frequencies, the previously demonstrated zero- or negative-refractive-index metamaterials have required the use of metallic inclusions, leading to large ohmic loss, a serious impediment to device applications^{20, 21}. Here, we experimentally demonstrate an impedance-matched zero-index metamaterial at optical frequencies based on purely dielectric constituents. Formed from stacked silicon-rod unit cells, the metamaterial has a nearly isotropic low-index response for transverse-magnetic polarized light, leading to angular selectivity of transmission and directive emission from quantum dots placed within the material.