Direct temperature dependence measurements of dark conductivity and two-beam coupling in LiNbO3:Fe

Direct measurements of dark conductivity were conducted over a broad temperature range in LiNbO(3):Fe. These measurements were performed on a series of crystals, which were cut from the same boule and subjected to different annealing procedures (oxidized, reduced, and as-grown). Activation energies of 0.5 eV and 1.1 eV were extracted from Arrhenius plots of the dark conductivity data. The location of the Fe(2+) energy level in the band gap was determined, and is in agreement with Born's principle. A correlation between the Maxwell relaxation times and the onset of a temperature-dependent reduction in two-beam coupling efficiency was observed.