Optical properties of borosilicate glass from 3.1 mm to 210 nm (0.4 meV to 5.89 eV) by spectroscopic ellipsometry

Borosilicate glass is of significant interest and utility to for a variety of applications, often for its robust ability to withstand significant thermal stresses resulting from a low coefficient of thermal expansion. Here, ellipsometric spectra of borosilicate glass from the millimeter wavelength range (terahertz) to the ultraviolet are collected from rotating compensator configuration ellipsometers. Specifically, spectra from three instruments each measuring a separate spectral range (0.4–4.1 meV; 0.035–0.75 eV; 0.75–5.89 eV) are modeled simultaneously. Continuous parameterization of the complex dielectric function (ε = ε₁ + iε₂) spectra from 0.4 meV to 5.89 eV describing the optical response of the glass is determined by modeling the measured spectra. Additionally, intensity-based transmittance measurement spanning 0.75–5.89 eV is used to determine the absorption coefficient at photon energies greater than 4 eV. Phonon absorption features are identified at low energies in the infrared and terahertz ranges.