Optical absorption and SHG in PMMA:DR1 thin films as function of poling time

Amorphous, PMMA: DR1 : surfactant and PMMA:DR1 :TEOS thin films were prepared by dip-coating. All films were calcined at 70°C for 3 hours. For nanostructured thin films two ionic surfactants were used, Sodium Dodecyl Sulfate (SDS) and Cetyltrimethyl ammonium bromide (CTAB) to obtain two different nanostructures of the PMMA matrix: lamellar, and hexagonal, respectively. X-ray diffraction studies were performed to determine the long-order structure tailored in the films. The measurements of the optical absorption and the second harmonic generation (SHG) intensity were carried out at different orientation arrangements of the chromophores embedded in the films. The chromophore orientation distributions were obtained by means of the corona technique. These distributions depend on the corona poling time. We physically modeled the optical absorption and the second harmonic generation experimental results as function of the corona poling time, employing only one fitting parameter related to the matrix-chromophore interactions. The physical model and the experimental results were in an excellent agreement. The experimental results fitted by the model are shown in plots of order parameter against corona poling time and SHG intensity against corona poling time. The amorphous films provide a larger SHG intensity values than those obtained from the nanostructured films. Thin films with lamellar structure have a SHG intensity bigger than those from hexagonal and PMMA:TEOS thin films.