Three-photon absorption in lithium tantalate measured by the Z-scan technique

Benabdelghani, Imene and Bazsó, Gábor and Tóth, György and Rácz, Péter and Dombi, Péter and Hebling, János and Polónyi, Gyula (2024) Three-photon absorption in lithium tantalate measured by the Z-scan technique. OPTICAL MATERIALS, 153. No.-115571. ISSN 0925-3467

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Abstract

Measurements have been carried out to investigate three-photon absorption (3 PA) coefficients in lithium tantalate crystals (LT) using the open-aperture Z-scan technique. This study employed a femtosecond laser pulse of 40 fs at 800 nm of central wavelength. The investigation was carried out on congruent LT crystal and stoichiometric LT crystals, having different Mg doping concentrations. Both ordinary and extraordinary polarizations were considered. The crystals were subjected to different pump intensities, ranging from approximately 120 to 480 GW/cm2. The measured z-scan curves have been evaluated by a pulse propagation model. The outcomes reveal that the dominant multi-photon absorption with this pumping wavelength is three-photon absorption (3 PA) and a decline of the 3 PA coefficient is demonstrated with increasing pumping intensity. Surprisingly, larger 3 PA coefficients were measured for LT than for LiNbO3 (LN), contrary to the larger bandgap of LT in comparison to LN. This suggests that LT has no advantage in comparison to LN in nonlinear optical applications if 800 nm pump pulses are used.

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