Optical damage in transition-metal-doped LiTaO3

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Abstract
The results of a detailed study of the optical damage in transition-metal (Fe, Cu, Mn, V, Cr, and Ni) -doped LiTaO3 are presented. The relationship between the sensitivity of the optical damage and the nominal concentration of dopants is analytically discussed based on the modified rate equations introducing trapping centers. The observed results of the dependence of sensitivity on nominal concentration, poling procedure, and heat treatment, and of the activation energy of the thermal decay and the distribution coefficients of examined transition metals in LiTaO3 are reported. The role of transition metals on optical damage is discussed using the results of electron paramagnetic resonance (EPR) and optical spectra in addition to the above results. It is found that Fe2+, Cu+, and oxygen vacancies, which stem from reduction or from off-stoichiometry, are mainly responsible for donors, and Fe3+, Cu2+, Mn3+, and V3+ play the role of trapping centers. In LiTaO3, the migration of oxygen vacancies by poling is very important, and is discussed in detail for Fe-doped LiTaO3. The optical damage for double-doped LiTaO3 containing Fe+Mn and Cu+Mn is also examined.