A new class of CdSe quantum dot-doped polymer films are synthesized using electrostatic layer-by-layer self-assembly processing technique. Transmission electron spectroscopy and electron beam diffraction results show that the diameter of the CdSe quantum dots is 2–3 nm and that the CdSe clusters possess a hexagonal structure. X-ray photoelectron spectroscopy allows determination of the concentration of the CdSe quantum dots within the resulting films. Linear electro–optic (Pockels) and quadratic electro–optic (Kerr) effect behavior of the films are investigated by using Mach–Zenhder interferometric and ellipsometric techniques, respectively. Linear electro–optic tensor ratios r333/r113 of 4.3±0.2 were determined. Theoretical calculations of the quadratic electro–optic coefficients are proposed for the conventional ellipsometric technique. The orientational enhancement effect originating from the permanent dipole moment and induced dipole moment of the CdSe clusters is also discussed. From the analysis of experimental data, we determine that the typical reorientational time for a CdSe dot in these films to respond to a sinusoidal electric field is 17.5 ms.

Purified single-walled carbon nanotubes are dispersed in two different types of polymer matrices. In these stable dispersed systems, the interaction between the polymer matrix and the single-walled carbon nanotubes, optical power limiting effect, and two-photon absorption are investigated. Transmission electron micrographs show the rigid polymer backbone interacts with the single-walled carbon nanotubes and results in the formation of nanoribbons and nanobundles in the dispersions. Optical measurements show that the nanoribbons and nanobundles significantly improve the optical power limiting performance through increased nonlinear optical absorption. Detailed comparison of optical power limiting, two-photon absorption, and two-photon excited fluorescence emission is presented. Our experimental results show that the different polymer backbones have a considerable effect on the nonlinear optical properties of carbon nanotubes.

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The spectrum and electro-optic properties of CdSe quantum dots are studied. Spectrum wavelength shifts that are due to the quantum size effect and to the electro-optic Stark effect are investigated. It is found that CdSe quantum dot-polymer composites formed by an electrostatic self-assembly (ESA) technique exhibit high internal electric fields. Using the second-order perturbation theory of the 1s-1s energy shift (Stark effect), we estimate the internal field of the ESA film to be as high as 2.6 ϫ 10 8 V͞m. This value results in a much higher absorption coefficient and electro-optic coefficients for ESA films than for their bulk crystal counterparts or for spin-coated film samples. The relationships among unusual spectra, film structure, and high electro-optic response are analyzed. These results are useful both for understanding the physical mechanisms of semiconductor quantum dots and for developing high-performance photonic devices.