The investigation of third-order hyperpolarizabilities and susceptibilities of push-pull azobenzene polymers

To estimate the potential for third-order nonlinear optical (NLO) properties of the title azobenzene polymers, the one-photon absorption (OPA) and two-photon absorption (TPA) characterizations have been determined by configuration interaction (CI) and time-dependent Hartree-Fock (TDHF) methods, respectively. The nonlinear absorption parameters (β) and third-order susceptibilities (χ⁽³⁾) have been measured by performing the Z-scan measurements. According to the ab-initio computation results, the investigated compounds exhibit averaged (isotropic) second hyperpolarizabilities (〈γ〉) with non-zero values, implying microscopic third-order optical nonlinearity. Our computed results on TPA cross-sections (δ(ω)), third-order hyperpolarizability and susceptibility values are in accord with the experimental observations of the examined molecules.