Picosecond z-scan investigation of two-photon absorption and bound electronic self-focusing in second-harmonic generation crystals

Wei Ji; He Ping Li; Feng Zhou; N. Zhai

doi:10.1117/12.252923

3 October 1996 Picosecond z-scan investigation of two-photon absorption and bound electronic self-focusing in second-harmonic generation crystals

Wei Ji, He Ping Li, Feng Zhou, N. Zhai

Author Affiliations +

Proceedings Volume 2897, Electro-Optic and Second Harmonic Generation Materials, Devices, and Applications; (1996) https://doi.org/10.1117/12.252923
Event: Photonics China '96, 1996, Beijing, China

Abstract

We present our investigation of two-photon absorption and self-focusing in second-harmonic-generation crystals on a picosecond 532-nm-wavelength beam using the z-scan technique. By measuring the crystal transmittance as a function of the crystal position with respect to the focus, the two-photon absorption coefficients were determined to be 0.041 plus or minus 0.008, 0.10 plus or minus 0.02, and 0.24 plus or minus 0.06 cm/GW for KTPA, KTA, and LiNbO₃, respectively. With inserting an aperture in front of the detector that recorded the transmitted laser pulse energy, self-focusing effects manifested themselves in the z scans on the three crystals at input irradiances of higher than a few GW/cm². The quantitative data confirm that the optical Kerr nonlinearity should be responsible for the observed self-focusing and n₂ equals (4.6 plus or minus 0.9), 3.6 plus or minus 0.7), and 5.3 plus or minus 1.0) multiplied by 10^-6 cm²GW in KTP, KTA and LiNbO₃, respectively. The microscopic origin of the measured n₂ can be understood in terms of bound electronic effects. The theoretical predictions are in agreement with our measurements. Finally, effects of the observed refractive nonlinearity on laser-induced damage are discussed.

Citation Download Citation

Wei Ji, He Ping Li, Feng Zhou, and N. Zhai "Picosecond z-scan investigation of two-photon absorption and bound electronic self-focusing in second-harmonic generation crystals", Proc. SPIE 2897, Electro-Optic and Second Harmonic Generation Materials, Devices, and Applications, (3 October 1996); https://doi.org/10.1117/12.252923

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