Two-photon absorption in undoped LiTaO3 crystals

The two-photon absorption (TPA) coefficient is obtained for pure lithium tantalate (LT) crystals as a function of CLi = 100% × Li2O/(Li2O + Ta2O5) ratio. Five LT samples with CLi = 47.95, 48.38, 48.75, 49.6 and 50 mol % were selected. The open Z-scan method was carried out to measure TPA coefficients at λ = 400 nm using 90 fs pulses at the appropriate pulse intensity of I0 = 3.5-4 GW/cm2. The TPA coefficients in LT drastically increase with the Li content increase and they reach 3-4 cm/GW for the stoichiometric composition LiTaO3. TPA exhibits its saturation behavior with the saturation intensity of 11 GW/cm2.