Investigations of nonlinear optical chromophores with femtosecond degenerate four-wave mixing in solutions

Time-resolved DFWM experiments were performed with 150 fs pulses at 800 nm in chloroform solutions of π-conjugated molecules: p-bis(o-methylstyryl)-benzene (Bis-MSB) and a newly synthesized derivative of distyrylbenzene: an oligomer of p-phenylenevinylene substituted in the para position with electron donating alkyleneoxy group bearing the methacrylic group and an electron accepting 2-ethylhexylsulfonyl group (MTPV-SOHE monomer). The asymmetric substitution causes a red shift (24 nm) of the absorption maximum and enhancement of third-order optical susceptibility. The second hyperpolarizability derived from a quadratic dependence of the phase matched DFWM signal on concentration of MTPV-SOHE was about 6 times bigger than that in Bis-MSB.