Anisotropy of two-photon absorption in BBO at 264 nm

Femtosecond pulses at lambda = 264 nm were used to measure the two-photon a bsorption (TPA) coefficient in beta -BaB2O4 (BBO) crystal. It was found tha t nonlinear absorption in BBO depends significantly on crystal cut and/or b eam polarization. For an ordinary beam propagating along the optical axis ( \ \c) and perpendicular to it (perpendicular toc) the similar values of TPA coefficient were obtained, namely (68 +/- 6) x 10(-11) and (66 +/- 7) x 10 (-11) cm/W. For an extraordinary beam (perpendicular toc) the TPA coefficie nt is significantly smaller, (47 +/- 5) x 10(-11) cm/W. (C) 2001 Elsevier S cience B.V. All rights reserved.