Periodically poling by chromophore molecule orientation control in cross-linked polymer film [for SHG]

We present a process for periodically poling using molecular orientation control in cross-linked polymer. Glycidylmethacrylate (GMA) was polymerized by 2,2´-azobisbutyronitrile in tetrahydrofuran at 60°C. for 1 hour. Poly-GMA dissolved in dimethylformamide containing nonlinear optical chromophore, disperse red 1 (DR1) or disperse orange 3 (DO3), and 4,4´-diaminodiphenylmethane as cross-linker was spin-coated on pyrex glass substrates. The films were dried and heat-treated for cross-linking at 100°C for 1 hour. The chromophore molecule was fixed in the crosslinked polymer network. To form a periodical structure the films were patterned by photolithography and reactive ion etching using O₂ plasma. Poly-GMA without cross-linker containing the chromophore was spin-coated to fill the etched grating grooves. The films were poled at 100°C for 1 hour. The films were periodically poled because the cross-linked part was not poled due to the raised transition temperature