Abstract: The nonlinear refraction indices n₂ and the reverse saturation absorption (RSA) coefficients β of a series of hydroxylphenyl porphyrins were measured by means of single beam Z-scan technique with a 8 ns laser pulse at 532 nm from which third-order nonlinear susceptibilities χ⁽³⁾ of the samples were calculated. The hydroxylphenyl porphyrins have a large value of the reverse saturation absorption and a large cubic nonlinear refractivity. The effects of molecular structures on the third-order nonlinear optical properties were discussed. The experimental results show that the effects of different numbers and different positions of the substituents on the nonlinear refractivity of the porphyrins are evident.

Key words: porphyrin, hydroxyphenyl porphyrin, Z-scan, third-order nonlinearity