Degenerate four-wave mixing studies of butadiyne-linked conjugated porphyrin oligomers

The third-order electronic susceptibilities have been measured in solution for a series of conjugated porphyrin oligomers, and for a conjugated polymer of this type. At 1064 nm, the non-resonant susceptibilities of the oligomers and the polymer are large (\chi((3))\ approximate to 10(-17)-10(-16) m(2) V-2), have comparable real and imaginary parts, and the real part is negative in sign. The molecular susceptibility per ring chromophore, (gamma/N), shows a linear dependence upon chain length, N. We propose a general mechanism for the enhancement of the third-order susceptibilities in conjugated porphyrin based materials due to two-photon resonance with charge transfer states. (C) 1999 Elsevier Science B.V. ALI rights reserved.