Proceedings PaperNonlinear optical properties of the main-chain-type liquid crystalline polymers and electric field effects: II
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The second harmonic generations (SHG) of liquid crystalline main-chain type polymers were investigated. The sample polymers are copolymers of 2-hydroxy-6-naphtoic acid with 4-hydroxy-benzoic acid, in various composition ratios. SHGs for the samples prepared by applying electric fields in some different manners at the liquid crystalline temperature were compared. The nonlinear optical coefficients dexp evaluated by Maker Fringe Method of electrically poled samples are 2-3 times larger than that of mechanically oriented sample whose dexp is about 5pm/V. Quasi-phase matching was performed by piling mechanically oriented thin films with alternatively directed machine direction. Using liquid crystal as the space between films and surfaces and tuning refractive index of the liquid crystals by applying adequate electric field, SH intensity increased up to 12-15 from one sheet of film.