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Dynamics of energy transfer and frequency upconversion in Tm 3 + doped fluoroindate glassComparative study of energy transfers from Er 3+ to Ce 3+ in tellurite and sulfide glasses under 980 nm excitation

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A complete structural phase diagram of annealed proton-exchanged X-cut LiTaO3 is presented, to relate refractive index change to proton-induced lattice deformation. From this diagram, explanations for the previously observed phenomena of index increase upon annealing and index decrease with increasing proton concentration (above a certain value) are derived. We have analyzed the evolution of index profiles during postexchange annealing, describing how the presence of multiple phases within a waveguide can lead to large index variations and buried index profiles. Finally, we identify at least two high-concentration phases that exhibit large temporal instabilities.

Annealed proton-exchanged wave guides in X-cut LiTaO 3 were characterized by infrared reflection and Raman scattering spectroscopy. The measured spectra were related to the multiple crystalline phases of H x Li 1Ϫx TaO 3 as identified by direct wave guide index profiling. Unique relationships were found to exist between the crystalline phases and corresponding spectra, which thus can be used to identify phase contents in a given wave guide. Vibrational bands of the studied spectra were correlated with the electro-optic properties of H x Li 1Ϫx TaO 3 phases. Phase-dependent anisotropy of protonic conductivity was predicted based on the observed polarization dependence of OH libration bands. Finally, the electro-optic coefficient r 33 was theoretically estimated for all phases and compared with previously reported experimental data.