Biaxial hyperbolic metamaterials

We have fabricated biaxial hyperbolic metamaterials (BHMMs) using layered structures consisting of titanium dioxide (TiO₂) and copper (Cu). In order to enable the biaxial property, an oblique angle deposition (OAD) technique is applied to deposit the dielectric layer. We have characterized the biaxial hyperbolic dispersion using variable angle spectroscopic ellipsometry (VASE) measurements in the wavelength range 400 nm to 900 nm. A noticeable difference be- tween in-plane permittivity components of the fabricated BHMM is observed to be 0.13 at 633 nm. The experimental characterization results have been in good agreement with the predictions of effective medium approximation (EMA) with an MSE of 18.