Nonlinear absorption properties of Cu(II)meso-tetra(4-sulfonatopheny1) porphine in TiO2/SiO2 organic-inorganic gel using Z-scan technique

The Cu(II)meso-tetra(4-sulfonatopheny1) porphines (Cu(II)-TPPS) with various concentrations are incorporated into TiO2/SiO2 to form organic and inorganic composite gels via sol-gel process. With a Nd:YAG laser of 532 nm wavelength and 7 ns pulse width, the curves of Z-scan are measured under the condition of open aperture. Nonlinear absorption parameters of these materials, which are attributed to the reverse saturation absorptions of monomer and dimer of Cu(II)-TPPS, are obtained by fitting the above curves with Z-scan theroy. The result indicates that the nonlinear parameter of gel increases with doping concentration increasing. The nonlinear absorption coefficients of gels in 1.11×10-4 mol/L A2, 1.48×10-4 mol/L A3 and 3.01×10-4 mol/L A4 doping concentration are 1.705×10-11, 1.892×10-11, and 4.854×10-11 m/W, respectively. The effects of monomer and dimer on the nonlinear parameter are discussed. The reduction of the nonlinear parameter results from the increases of dimer and multimer as the doping concentration increases. The damage threshold of the gel is also measured and can reach up to 5 J/cm2.