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We demonstrate a single-shot pump-probe technique in a single-beam basis. A transmissive annular echelon is used to spatially encode a single pulse, and generates a pump pulse and a probe pulse train with approximately 8 ps delay time and 40 fs time interval. Using this technique, we studied the ultrafast absorption dynamics of ZnSe at a wavelength of 515 nm. And our results indicate the ZnSe has an ultrafast two-photon absorption process and a slow carrier absorption process at 515 nm. In addition, with the help of a neutral density filter (ND), we also investigated the effect of probe intensity on the experimental results. [ABSTRACT FROM AUTHOR]

Four sandwich phthalocyanines with different rare earth metals (La, Y, Yb and Sc) are synthesized to investigate the influence of aggregation on nonlinear optical limiting effect. Hyperchem fitting results show that the distance between the phthalocyanine rings of the four phthalocyanine compounds is 2.81, 2.69, 2.56 and 2.38 Å for LaPc (Tetra-β-(4-nitro) lanthanum phthalocyanine), YPc (Tetra-β-(4-nitro) yttrium phthalocyanine), YbPc (Tetra-β-(4-nitro) ytterbium phthalocyanine) and ScPc (Tetra-β-(4-nitro) scandium phthalocyanine), respectively. As the radius of rare earth ions decreases, the interlayer spacing between phthalocyanine rings decreases, which greatly increases the degree of aggregation between phthalocyanine rings. As a result, the photophysical and nonlinear absorption coefficients of different rare-earth phthalocyanines also show regular changes. The nonlinear absorption coefficients of the four rare-earth phthalocyanines were LaPc (β = 1.86ⅹ10−10 m/W), YPc (β = 9.78ⅹ10−11 m/W), YbPc (β = 6.63ⅹ10−11 m/W), ScPc (β = 7.43ⅹ10−11 m/W), respectively, indicating that the degree of aggregation between phthalocyanine rings gradually increases as the radius of rare earth metals changes from La, Y, Yb, to Sc, which inhibits the reverse saturable absorption process of the triplet states, resulting in a gradual decrease of the nonlinear absorption coefficient. The experimental results fully reveal the effect of the aggregation effect between phthalocyanine rings on photophysical and nonlinear optical properties, and would provide a theoretical basis for the design of high-performance nonlinear optical materials. Image 1 • Sandwich phthalocyanines with different metals (La, Y, Yb, Sc) are designed to investigate the effect of aggregation on nonlinear optical effect. • Results show that the distance between the phthalocyanine rings are 2.81, 2.69, 2.56 and 2.38 Å for LaPc, YPc, YbPc and ScPc, respectively. • As the metal ion radius decreases, the aggregation effect between phthalocyanine rings increases, which results in worse NOL behaviour. • The influence of aggregation on structural, photophysical and NOL properties was obtained by adjusting the distance between phthalocyanine rings. [ABSTRACT FROM AUTHOR]