Vacuum deposition of nonlinear chromophore-polymer composite thin films

Novel nonlinear composite thin films containing 4-dialkylamino-4′-nitro-stilbene (DANS) and Teflon AF 1600 have been deposited by vacuum evaporation techniques. Pure DANS thin film, due to its centrosymmetric crystal structure, does not exhibit any electro-optic effect. However, composite thin films of DANS and Teflon AF 1600 with a DANS concentration of 5%–25% (by volume) do exhibit an electro-optic effect after poling. Their electro-optical coefficients are measured to be as large as 2.4 pm/V. X-ray diffraction shows that these composite thin films are in an amorphous state as-deposited as well as after poling. It is argued that the DANS molecules are in their molecular form embedded in the Teflon AF amorphous matrix, thereby allowing the effect of their large molecular hyperpolarizability to be detected. The characterization of the thin films using scanning electron microscopy is also presented.