ABSTRACT
We synthesize colloidal HgSe quantum dots and characterize their nonlinear refraction and nonlinear absorption using a Nd:YAG laser and its second harmonic. The 7.5â nm quantum dots were synthesized using the hot-injection method. The nonlinear absorption (ß = 9×10-7 cm W-1) and negative nonlinear refraction (γ = -5×10-12 cm2 W-1) coefficients of colloidal quantum dots were determined using the 10â ns, 532â nm laser radiation. The joint influence of above processes was realized at a higher intensity of probe pulses. In the case of 10â ns, 1064â nm radiation, only negative nonlinear refraction dominated during z-scans of these quantum dots. The studies of optical limiting using two laser sources demonstrated the effectiveness of this process at 532â nm. The role of nonlinear scattering is analyzed. We discuss the mechanisms responsible for the nonlinear refraction processes in colloidal HgSe quantum dots.