Measurement of third-order nonlinearities of side-chain-substituted polymers

Optical third harmonic generation at 1.904, 1.579 and 1.064 μm experiments have been performed on thin films fabricated from side chain polymers containing effectively 4-dialkylamino-nitro-benzene, 4-dialkylamino-4′-nitro-stilbene, 4-dialkylamino-4′-nitro-diphenylbutadiene, 4-dialkylamino-4′-nitro-diphenylhexatriene as the side groups. We have measured values of χ (3) (−3ω; ω, ω, ω) in the range of 0.54 × 10 −12 to 7.42 × 10 −12 esu, at 1.904 μm incident radiation, which are comparable to the nonresonant values found in fully conjugated back-bone polymers [1]. The values of χ (3) at both 1.904 and 1.579 μm change by a factor of 15 as the conjugation length is increased.