Making light go infinitely fast

Impedance-matched metamaterials with zero refractive index can be achieved by exploiting a Dirac cone at the center of the Brillouin zone. We present an in-plane Dirac-cone metamaterial consisting of low-aspect-ratio silicon pillar arrays in an SU-8 matrix with top and bottom gold layers. Using an integrated nano-scale prism constructed of the proposed material, we demonstrate unambiguously a zero refractive index in the optical regime. This design serves as a novel on-chip platform in the optical regime to explore the exotic physics of Dirac-cone metamaterials and to implement applications of Dirac-cone metamaterials in integrated photonics, including super-coupling and modulation.