Ultrafast and Large Third-order Nonlinear Optical Properties of CdS Nanocrystals in Polymeric Film

TL;DR

This paper demonstrates that CdS nanocrystals embedded in polymeric films exhibit ultrafast, large third-order nonlinear optical properties, making them promising for optical switching applications.

Contribution

The study reports the synthesis and characterization of CdS nanocrystals in polymeric films with ultrafast, large third-order nonlinearities at 800 nm, including measurements of two-photon absorption and Kerr effects.

Findings

High two-photon absorption coefficient and Kerr coefficient measured.

Nonlinearities recover within approximately 1 ps.

Potential for optical switching applications demonstrated.

Abstract

We report the ultrafast and large third-order nonlinear optical properties of CdS nanocrystals (NCs) embedded in a polymeric film. The CdS NCs of 2-nm radius are synthesized by an ion exchange method and highly concentrated in the two layers near the surfaces of the polymeric film. The two-photon absorption coefficient and the optical Kerr coefficient are measured with laser pulses of 250-fs duration at 800-nm wavelength. The one-photon and two-photon figures of merit are determined to be 3.1 and 1.3, respectively, at irradiance of 2 GW/cm2. The observed nonlinearities have a recovery time of ~ 1 ps. The two-photon-generated free carrier effects have also been observed and discussed. These results demonstrate that CdS NCs embedded in polymeric film are a promising candidate for optical switching applications.