Preparation And Performance Study Of The Nonlinear Optical Thin Film Materials Dcdhf-2-v/pmma

Nonlinear optics, as a new subject, has showed great application foreground in the fields of modern laser technology, optical communication, data storage, optical information processing, etc. in the past decades. The organic polymer has developed rapidly and attracted considerable attentions by scientific research institutions, companies and military, due to its superior NLO characteristics compared with inorganic materials.Several mainly used NLO materials were reviewed in this thesis, second-order organic polymer NLO materials and their latest progress were recited. The first hyperpolarizabilities of DCDHF-2-V was calculated by using the base of 6-31G and the closed shell restricted Hartree-Fock method, which was implemented by the quantum chemistry software Gaussian03. The result of the calculation was 62.508×10-30esu. The chromophore molecules were doped in poly (methyl) methacrylate (PMMA) and typical spin-casting techniques were used for depositing the polymer thin films. Details of purification of the polymer, cleanouting of the substrate, preparing of the solution and the process of spin-casting techniques were described in this thesis. Some methods of obtaining second-order NLO materials with noncentrosymmetric structure as well as all-optical poling were introduced. In order to induce macroscopical noncentrosymmetric polar order, the films were corona-poled in this paper.The order parameterφwas gained as a value of 31.45% by investigating the UV/Visible absorption spectra of the unpoled and poled polymer films. The Atomic Force Microscopy (AFM) images of the polymer films showed that the surface of the film sample is extremely flat and clean. The film morphology was greatly changed after poling, meanwhile, numerous hills were found and aligned along with the poling direction. As time passed by, the peak of absorption increased a bit while the hills on the film surface turned to be smooth as a result of the decay of the dipole alignment. The refractive index and the thickness of the film were measured by ellipsometer. The propagation modes of the light with different wavelength were investigated using the plots method based on the ellipsometer measurement. The measuring principle of the second-order nonlinear coefficient with Maker-fringe method was introduced. The second-order nonlinear coefficient d33 of DCDHF-2-V/PMMA obtained from Maker-fringe method was 17.2 pm/V. One-dimensional rigid orientation gas model (1DROGM) was also used to calculate the nonlinear coefficient d33 and the result was 26.4 pm/V, according to the calculatedβvalue from quantum chemistry theory calculation.