Monolithic photorefractive molecule with excellent transparency in the visible region

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Abstract
9-(2-Ethyl-hexyl)-3-[2-(4-methanesulfonyl-phenyl)vinyl]- 9H -carbazole (EHCS) was synthesized as a monolithic photorefractive molecule forming low T g (∼25 ° C ) organic glass. It showed distinct photoconductivity due to the carbazole moiety and the optical nonlinearity by the push–pull structure. The EHCS glass showed excellent optical quality and great stability as the ethylhexyl group effectively suppressed the crystallization in the films. Also, the extremely simple structure of EHCS contributed to a very high chromophore concentration. This single-component photorefractive glass of EHCS showed large net gain (56.3 cm−1) and diffraction efficiency (12%). Photorefractivity of EHCS glass was greatly improved by doping with a small amount (<1%) of 2,4,7-trinitrofluorenone (TNF). The two-beam coupling gain of samples with TNF was 113 cm−1 and the diffraction efficiency was 29%.