Nonlinear optical properties of colloidal CdSe/ZnS quantum dots in PMMA

The colloidal CdSe/ZnS quantum dots (QDs) in the PMMA polymer film with different QDs concentrations were fabricated. The influence of QDs concentration and excitation pump energy on nonlinear optical (NLO) properties of PMMA capped CdSe/ZnS QDs was investigated by the Z-scan technique with nanosecond laser pulses in the near-infrared spectral band. A large effective nonlinear absorption coefficient (β _eff  ∼ -10^-13 esu) due to the saturable absorption was observed. It was found that the appropriate concentration could lead to the reinforcement of NLO effect. In addition, the impact of the excitation energy on the nonlinear refractive index n ₂, real and imaginary parts of the third-order nonlinear optical susceptibility was also performed. This study involving the light-matter interactions in the colloidal quantum dots will benefit potential NLO-based applications of optoelectronics, optical modulation and photonics.