Third Harmonic Generation in Precursor Route Poly(p-Phenylene Vinylene)

From third harmonic generation measurements on unoriented thin films and with excitation at 1.064 µm we have determined a third order nonlinear susceptibility χ (3) (-3ω; ω, ω, ω) of 7.5 ×10 -11 esu for poly(p-phenylene vinylene) [PPV]. In addition, the effect of increasing π-electron conjugation has been investigated for samples at different stages in the thermal conversion from saturated precursor to fully conjugated polymer. χ (3) increases in magnitude with increasing conversion as is expected for a nonlinearity originating in the conjugated π-electron system.