The microstructural difference between proton-exchanged LiNbO3 and LiTaO3 crystals by Raman spectroscopy

By means of a conventional Raman scattering technique, Raman spectra of proton-exchanged LiNbO3 (PELN) and LiTaO3 (PELT) crystals were examined as a function of PE time. The experimental result was that the relative intensities IE(TO)/IA1(TO) reach maxima and minima in PELN and PELT with about 12 and 8 h proton treatment, respectively, when y-surface cracks are visible. This phenomenon, together with the different extraordinary index changes reported previously, reflects the microstructural difference between PELN and PELT. This difference mainly arises from both the different displacements of positive ions along the optical z axis in bulk and the different proton distributions in the exchange layer due to PE. (author)