Refractive index change and Raman scattering of Z-cut proton-exchanged LiTa
O3 optical waveguides with different composition have been studied. Probing
of the waveguide depth was carried out by using micro-Raman spectroscopy i
n order to distinguish layers with different phase states. Varying the prot
on-exchange and post-exchange annealing regimes, two phases - alpha and bet
a - in addition to the pure LiTaO3, were clearly observed. The behaviour of
the A(1) vibrations of the TaO6 groups was found to be very sensitive to t
he phase changes. Using data from waveguide Raman spectra, normal and obliq
ue E(TO, LO) phonons were sorted and their properties were followed in the
alpha and beta phases. The OH-stretchings are considered to correspond to d
ipoles turned out of the oxygen planes.