Photoinduced phase-matched second-harmonic generation in azodye-doped polymer films

Phase-matched second-harmonic generation (SHG) in azodye-doped polymethylmethacrylate films was demonstrated using the nonresonant optical poling technique. During the seeding process, samples were irradiated simultaneously by coherent superposition of the fundamental and the second-harmonic light of a femtosecond laser. Optical poling experiments were performed at three wavelengths of 1500, 1320, and 1300 nm, respectively. The quadratic dependence of SHG on the film thickness showed that a chi ((2)) grating that satisfied the phase-matching condition for SHG was optically induced in the polymer films. The SHG conversion efficiency of a 105 mum thick film was estimated to be about 2%. A relaxation retardation effect of the photoinduced chi ((2)) was also observed in the thick films. (C) 2001 American Institute of Physics.