Optical properties of single-crystal Gd3 Ga5 O12 from the infrared to ultraviolet

Optical properties of commercially available gadolinium gallium garnet (Gd3Ga5O12) single crystals have been studied over a spectral range from 0.034 to 5.887 eV using spectroscopic ellipsometry and transmittance measurements via a near infrared to ultraviolet spectral range multichannel ellipsometer and a Fourier transform infrared (FTIR) ellipsometer. The complex dielectric function (ϵ = ϵ1 + iϵ2) spectra from 0.034 to 5.887 eV have been determined. Transmission measurements have been performed to more accurately extract the absorption coefficient near the band edge and identify sub band gap features. Analysis of ϵ for Gd3Ga5O12 indicates a direct band gap at 5.66 ± 0.01 eV, sub band gap absorption features from 3.95 to 5.06 eV, and nine transverse optical phonon modes at 288, 313, 329, 361, 370, 467, 577, 609, and 670 cm−1 and longitudinal optical phonon modes at 288, 327, 338, 370, 461, 490, 592, 663, and 707 cm−1.