Nonlinear optical characterization of Disperse Orange 3

The nonlinear optical responses of Disperse Orange 3 (DO3) dissolved in tetrahydrofuran (THF) with different concentrations were investigated by Z-scan D4σ technique employing 12 ps and 17 ps pulses of Nd:YAG laser at 532 nm and 1064 nm, respectively. The comparison of the experimental results at both wavelengths demonstrates the strong influence of the resonant phenomena related to the linear absorption on the nonlinear response at 532 nm. In particular, DO3 solution was found to exhibit negative resonant nonlinear refraction with negligible saturable and multi-photon absorption. Moreover, the competition between negative and positive nonlinear refractive indices (n2) of the solute and the solvent was observed at low concentrations. The linear dependence of n2 on the latter quantity allowed to estimate an effective second-order hyperpolarizability of DO3 molecule at 532 nm.