Optical properties of NAEC-PMMA nonlinear polymeric thin film

Novel guest nonlinear optical (NLO) chromophore molecules (4-nitrobenzene)-3-azo-9-ethylcarbazole (NAEC) were doped in poly (methyl methacrylate) (PMMA) host with a concentration of approximately 15% by weight. For a useful macroscopic electro-optic (EO) effect, these NLO molecules NAEC were arranged in a noncentrosymmetric structure in the host polymer by corona-onset poling at elevated temperature (COPET). For applying NAEC-PMMA polymer in optical devices such as EO switch, its optical properties have been investigated. The UV/Visible absorption spectra for the unpoled and poled polymer film were determined. The refractive index of the film was also determined from measurements of the coupling angles with the reflective intensity at 632.8 nm wavelength. Using the simple reflection technique, the EO coefficient ₃₃ value was measured as 60 pm/V at 632.8 nm wavelength. The second-order nonlinear coefficient d₃₃ was characterized by the second-harmonic-generation (SHG) experimental setup and the calculated d₃₃ value reached 18.4 pm/V at 1064 nm wavelength. The relation between the second-order nonlinear coefficients d₃₃ and d₁₃ for the poled polymer film was also discussed in detail and the ratio d₃₃/d₁₃ value was obtained as 3.3.