Synthesis of High-Tg Azo Polymer and the Optimization of its Poling Condition for Stable EO System

<jats:title>Abstract</jats:title><jats:p>A new material for second-order nonlinear optics was synthesized, which was a copolymer of N-phenylmaleimide, 4-isopropenylphenol and 4'-[N-ethyl-N-(4-isopropenylphenoxyethyl) amino]-4”-nitroazobenzene (PMPD). PMPD films were poled by corona-poling technique. The optical nonlinearity of poled PMPD was measured by second harmonic generation (SHG) and electro-optic (EO) effect, and it was demonstrated that this polymer had large optical nonlinearity and a very long-time stability, as was expected. These properties were thought to be sufficient enough for practical EO devices. On the other hand, from the viewpoint of the sample preparation technique, poling conditions were investigated in order to achieve the highest possible dipolar orientation. As a result, it was found that the relationship between the electric resistance of polymer film and substrate was a critical factor for corona-poling efficiency. From a simple model, it was suggested that the poled PMPD film prepared onto the glass substrate with a resistance of ˜0.8 GΩ (at 160 °C) exhibits large SHG and EO coefficients, more than ˜500 × 10<jats:sup>−9</jats:sup> e.s.u (d<jats:sub>33</jats:sub> at λ = 1.064 μm) and ˜70 pm/V(r<jats:sub>33</jats:sub> at λ = 632.8 nm), respectively. It should be noted that this expected values are approximately twice as much as obtained under conventional corona-poling conditions.</jats:p>