Nonsymmetrical transition from reverse-saturable absorption (RSA) to saturable absorption (SA) caused by excited state absorption induced mass transport of the CuPcTs dissolved in dimethyl sulfoxide is observed in an open aperture Z-scan experiment with a 21-ps laser pulse. The nonsymmetrical transition from RSA to SA is ascribed neither to saturation of excited state absorption nor to thermal induced mass transport, the so-called Soret effect. In our consideration, strong nonlinear absorption causes the rapid accumulation of the non-uniform kinetic energy of the solute molecules. The non-uniform kinetic field in turn causes the migration of the solute molecules. Additionally, an energy-gradient-induced mass transport theory is presented to interpret the experimental results, and the theoretical calculations are also taken to fit our experimental results.
The title cluster compound [WS4Cu3Br(bipy)2] has been synthesized by the reaction of (NH4)2, CuBr and 2,2′ bipy in DMF solution. Single crystal X ray diffraction data show that the compound has a nest shaped structure. Nonlinear optical properties (NLO) of the cluster were investigated by a Z scan technique with a pulsed laser at 532nm. The cluster exhibits the strong NLO absorption and a self defocusing effect (effective non linear absorption coefficient, α2eff=7.3×10-11mW-1; effective non linear refractive index, n2eff=3.9×10-11esu) when measured in a 6.0×10-4mol·dm-3 DMF solution. CCDC: 200397.
A very simple technique, by which both the magnitude and the sign of nonlinear refraction can be determined through using only one single pulse and beam with a phase object, is presented. Using this technique, only the transmittance of an aperture in the far field is investigated. We study the nonlinear refraction of the carbon disulfide by using the presented technique with 21 ps pulses at a wavelength of 532 nm as a test.
Nonlinear refractive properties of chloroaluminum phthalocyanine(CAP) in ethanol solution are studied using the Z-scan technique with picosecond(ps) and nanosecond(ns) laser pulses at a wavelength of 532 nm.A transition from self-focusing to self-defocusing in CAP solution excited by 10 ns pulses is observed during the decrease of its concentration.This transition is due to co-existing excited-state refraction and transient thermal lensing effects.The experimental results are described very well using the rate-equation model and the theory of transient thermal refraction in liquids.The refractive cross sections of the excited-state are also obtained.
