Molecular second hyperpolarizability measured in cumulene-containing polymers

Nonlinear optical susceptibilities were measured in a cumulene-containing polymer using the Z-scan technique at 1064 780 and 590 nm, respectively. At off resonance conditions we obtained real (Re) and imaginary (Im) orientationally averaged second hyperpolarizability γ from a straightforward Z-scan analysis using CS2 as our standard; we got Rey=−6.2 × 10−30 esu at 1064 nm and γ=(−2 + 0.261) × 10−30 esu at 780 nm. Measurements at 590 nm were accompanied by one-photon absorption saturation, which could be mathematically extracted from the overall γ, leaving only the nonresonant terms. We thus obtained at 590 nm γ=(−1.4 + 2.21) × 10−29 esu. The two orders of magnitude increase in Imγ from 780 to 590 nm is discussed within the summation of states model.