Negative-index bianisotropic photonic metamaterial fabricated by direct laser writing and silver shadow evaporation.

We present the blueprint for a novel negative-index metamaterial. This structure is fabricated via three-dimensional two-photon direct laser writing and silver shadow evaporation. The comparison of measured linear optical spectra with theory shows good agreement and reveals a negative real part of the refractive index at around 3.85 microm wavelength -- despite the fact that the metamaterial structure is bianisotropic owing to the lack of inversion symmetry along its surface normal.