Optical anisotropy and refractive index dispersion of Zn ₂ GeO ₄ microrods

Dielectric resonators with high light confinement offer low optical losses, which is essential for the development of high-performance optoelectronic devices. Among the different compounds, Zn ₂ GeO ₄ has emerged as a promising wide band gap transparent conductive oxide with a low-dielectric constant. In order to control and optimize their optoelectronic properties, a good knowledge of their optical constants, such as the refractive index, is required. Here, we exploit the behaviour of Zn ₂ GeO ₄ microrods as optical cavities to estimate experimentally for the first time, so far as we know, the refractive index dispersion of this compound. In addition, first principle calculations by density functional theory (DFT) of the dielectric function as a function of the light propagation direction have been performed, which have revealed a strong optical anisotropy. The results show that there is also an influence of native defects on the optical propagation properties. These physical aspects are crucial to tailor the optical features of Zn ₂ GeO ₄ and exploit them in optoelectronic devices with bespoke properties.