THE 3RD-ORDER NONLINEAR-OPTICAL PROPERTIES OF PORPHYRIN OLIGOMERS

Using a single beam z-scan technique with a 30 ps laser pulse at 640 a nd 1064 nm, the real and imaginary parts of the third-order nonlinear optical susceptibilities of porphyrin oligomers for different numbers of repetition units in solutions were measured. At a probe wavelength 640 nm, the real parts of chi((3)) (R chi((3))) of oligomers which con sist of porphyrins bridged by 1,4-phenylene moiety were found to be ne gatively enhanced significantly compared with that of the monomer. Whi le Re chi((3)) of the oligomers increased with increasing the porphyri n unit, the value per monomer unit remains almost constant; that is, R e chi((3)) is proportional to the number of monomer units. The oligome rs in which the porphyrin rings are directly attached together at the meso position exhibited enhanced imaginary parts of chi((3)) at 640 an d 1064 nm. The enhanced real part was also detected at 1064 nm. These unique properties are discussed in terms of the two photon resonance p rocess. (C) 1997 American Institute of Physics.