Abstract
The paper demonstrates photorefractive characteristics of the aromatic polyimide <$>(T_g=230\,^\circ\hbox{C})<$> containing J-aggregates of the thiacarbocyanine dye. The two wavelengths <$>647\,\hbox{nm}<$> and <$>514\,\hbox{nm}<$> of Ar-Kr-laser were used. The J-aggregates of the dye are responsible for optical absorption at <$>647\,\hbox{nm}<$>. At that wavelength the net gain coefficient increases from <$>\Gamma-\alpha=217\,\hbox{cm}^{-1}<$> to <$>361\,\hbox{cm}^{-1}<$> with growth of external electric field <$>E_0<$> from 16 to <$>123\,\hbox{V}/\rmu\hbox{m}<$>. Only samples containing J-aggregates exhibit the PR effect at wavelength <$>514\,\hbox{nm}<$> at which the laser excites monomeric form of the dye. The estimated at <$>514\,\hbox{nm}<$> and <$>E_0=16\,\hbox{V}/\rmu\hbox{m}<$> two-beam gain coefficient is near <$>480\,\hbox{cm}^{-1}<$> and the net gain <$>\Gamma-\alpha<$> is about <$>118\,\hbox{cm}^{-1}<$>. The high glass temperature of aromatic polyimide should appreciably limit the orientational effects at room temperature and the third order non-linearity could mainly determinate the PR effect.
Published Version
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