We develop an open-aperture ͑OA͒ Z scan and nonlinear transmission theory of two-photon-induced excited-state absorption, under the excitation of spatial Gaussian laser pulses with temporal Gaussian and hyperbolic secant profiles. The found analytic expressions allow us to straightforwardly fit the OA Z-scan trace and the nonlinear transmission curve, for convenient extraction of the nonlinear absorption coefficients. As a test, the two-photon-induced excited-state absorption in a chalcone derivative of 3,4-dimethoxy-4Ј-fluorochalcone is explored by performing femtosecond Z-scan measurement and is analyzed by our theory.

By performing both Z-scan and transient transmission measurements with 130 fs laser pulses in the near infrared region, we investigated structure-property relationships for χ(3) in acceptor-substituted 3,4,5-trimethoxy chalcone derivatives. We determined all nonlinear parameters, including two-photon absorption (2PA) cross section, 2PA-induced excited-state absorption (ESA) cross section, microscopic second-order hyperpolarizability, and lifetime of the excited state in these molecules. We found that the microscopic second-order hyperpolarizability γR and 2PA cross section σ2PA in chalcone derivatives increase as the acceptor strength of the molecules increases, which demonstrates an enhancement in optical nonlinearities by simple structural variations. We evaluated the one-photon, two-photon, and effective three-photon figures of merit for acetone solutions of chalcone derivatives at irradiance of 100 GW/cm2. Furthermore, we observed optical limiting behavior in these compounds, which result from both 2PA and 2PA-assisted ESA. These results indicated that chalcone derivatives are a promising candidate for applications on nonlinear photonic devices.

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In the title compound, C 14 H 10 ClN 3 O 3 ·H 2 O, the benzohydrazide group is not planar and the mol­ecule exists in a cis configuration with respect to the methyl­idene unit. The dihedral angle between the two substituted benzene rings is 38.7 (3)°. In the crystal structure, mol­ecules are linked by O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonds into a two-dimensional network parallel to the (100) plane. The crystal structure is further stabilized by weak C—H⋯O inter­actions.

Key indicators: single-crystal X-ray study; T = 100 K; mean (C-C) = 0.002 Å; R factor = 0.043; wR factor = 0.107; data-to-parameter ratio = 17.3.In the title compound, C 8 H 11 N 2 S + ÁC 12 H 10 NO 3 S À , the NH group of the S-benzylthiuronium is protonated and the interplanar angle between the phenyl ring and the CH 2 -S C(NH 2 ) 2 unit is 47.44 (10) . In the 4-anilinobenzenesulfonate anion, the interplanar angle between the two rings is 44.07 (8) . In the crystal structure, anions are linked into chains along the c-axis direction by N-HÁ Á ÁO hydrogen bonds, while additional N-HÁ Á ÁO interactions link the cations to the anions in chains along the b-axis direction. These chains are further interconnected into a two-dimensional network parallel to the bc plane by C-HÁ Á ÁO interactions. C-HÁ Á Á contacts are also observed. Related literature

Key indicatorsSingle-crystal X-ray study T = 100 K Mean (C-C) = 0.003 Å R factor = 0.024 wR factor = 0.058 Data-to-parameter ratio = 21.2 For details of how these key indicators were automatically derived from the article, see