Optical nonlinearity and optical limiting of CdSeS/ZnS quantum dots

Abstract

CdSeS/ZnS quantum dots (QDs) were synthesized through the chemical route. The optical limiting behavior of these QDs was observed. The quantum dots’ nonlinear absorption and nonlinear refraction were investigated by the Z-scan technique using a Nd:YAG laser second-harmonic radiation (λ = 532 nm, t = 35 ps). Based on the absorption and fluorescence spectra, it is reasonable for us to infer that the nonlinear absorption arises from free carrier absorption (FCA). These QDs have average absorption cross-section of 1.26 × 10⁻¹⁶cm² and nonlinear refractive index in the order of 10⁻⁸esu. The large nonlinear absorption perhaps allows them to be candidate material for the optical limiting devices.

Keywords:

• Z-scan technique
• free carrier absorption
• absorption cross-section

Acknowledgments

This research was supported by the Science Foundation of Key Laboratory of Opto-electronics Information Technical Science of Ministry of Education, Institute of Modern Optics, Nankai University, China.