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, hgh xxxxi and hgh xyyxi, 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 (hgh xyyxi/hgh xxxxi) of the hyperpolarizabilities was 0.26, which indicated a large contribution of an electronic polarization process to the third-order nonlinearity of CdTe NCs.