Third-order optical nonlinearities in new octupolar molecules and their dipolar subunits

The third nonlinear optical susceptibility $({\chi }^{〈3〉})$ of a new family of octupolar molecules with one, two, and three double bonds has been measured at 532 in tetrahydrofuran solutions by the degenerate four-wave mixing (DFWM) method. For comparison, we also measured the analogous dipolar subunits of the molecules. The second hyperpolarizability (γ) for these molecules was deduced. We found that octupolar molecules exhibit large second-order hyperpolarizability (γ) values. The γ values obtained for octupolar compounds are approximately 10 times larger than those of their corresponding dipolar subunits and ${10}^4$ times larger than those of ${\mathrm{CS}}_2,$ which is a reference material for DFWM.