OPTICAL ANISOTROPY OF SRLAALO4 AND SRLAAL0.75GA0.25O4 SINGLE-CRYSTALS

The optical response of uniaxial SrLaAlO4 (SLA) and SrLaAl0.75Ga0.25O4 (SLAG) single crystals is investigated by several techniques - ellips ometry, reflectance, and transmittance. The optical constants in the U V-VIS region have been obtained from the reflectance and transmittance spectre. A novel method of measurements of the birefringence by spect roscopic ellipsometry is reported. The resulting refractive indices fo r both polarizations are compared with precise standard measurements p erformed using a single wavelength null ellipsometer. The reflectivity of SrLaAlO4 crystals is obtained for both polarizations in the infrar ed region. The fit of the spectra in terms of Lorentzian oscillators p rovides a quantitative comparison of the phonon mode parameters with t hat of LaAlO3, and reveals a strong anisotropy of the lattice vibratio ns polarized along the optical axis and perpendicular ro it.