In situ investigation of optical absorption changes in LiNbO3 during reducing/oxidizing high-temperature treatments

This paper presents experimental results of an in situ investigation of optical absorption of congruent lithium niobate during reducing (95% Ar+5% H2) and oxidizing (O2) high-temperature treatments in the temperature range from 20 to 800 deg. C. The absorption spectra measured at in situ conditions at high temperatures in reducing/oxidizing atmospheres as well as the kinetics recorded at fixed wavelength during rapid replacement of gas atmospheres have been analysed. The origin of the changes in optical absorption caused by the redox treatments is discussed in terms of hydrogen and oxygen ion diffusion and the point defect structure of the material