The second hyperpolarizability of CdTe nanocrystals using polarization-resolved degenerate four-wave mixing

Polarization-resolved forward degenerate four-wave mixing (DFWM) in a nonresonant region revealed the effective third-order nonlinear susceptibility of colloidal CdTe nanocrystals (NCs) with the size near the Bohr radius and various concentrations. The second hyperpolarizabilities, 〈γxxxxh〉 and 〈γxyyxh〉, of the CdTe NCs were ∼1.15 × 10−41 m5/V2 and ∼3.01 × 10−42 m5/V2 from the measurement of the concentration-dependent third-order nonlinear susceptibility of CdTe NCs, respectively. The ratio (〈γxyyxh〉/〈γxxxxh〉) of the hyperpolarizabilities was ∼0.26, which indicated a large contribution of an electronic polarization process to the third-order nonlinearity of CdTe NCs.