Anisotropic Terahertz Permittivity of β-Ga2O3

We report on the anisotropy of the terahertz permittivity of β-Ga
₂
O
₃
through terahertz transmission measurements in single crystals of (010) and (-201) orientation. The electromagnetic wave propagation in this anisotropic crystal is best described with an orthogonal set of eigenmodes, i.e., polarization eigenvectors, wherein each eigenmode possess a distinct refractive index. Polarization-dependent transmission measurements were carried out to ascertain the nature of the eigenmodes and their directions with respect to the crystal axes.