Composition-tunable nonlinear optical properties of ternary CdSexS1−x (x = 0–1) alloy quantum dots

Abstract

Based on the synthesis of high-quality ternary CdSe_xS_1−x quantum dots (x = 0–1) with uniform size by a simple modified one-pot method, the composition-tunable nonlinear optical properties of ternary CdSe_xS_1−x alloy quantum dots were, for the first time, investigated by the Z-scan technique using 532 nm laser radiation. It was found that when the x values in CdSe_xS_1−x were changed from 0 to 1 the absolute values of the nonlinear refractive index (n₂) and nonlinear susceptibility (χ⁽³⁾) increased 4–10 times. The composition-tunable nonlinearity should be attributed to the enhancement of resonance, due to the gradual decrease of the lowest direct band gaps of CdSe_xS_1−x QDs with the increase of the Se content.