Photorefractive effects observed in 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium toluene-p-sulfonate

We measured, for the first time to our knowledge, a net two-beam coupling gain in an organic crystal. Our photorefractive measurements were carried out in nominally pure organic crystals of 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium toluene-p-sulfonate (DAST). Because of its large electro-optic coefficient, r(11) = 83 pm/V at lambda = 750 nm, and a photoconductivity of up to sigma = 6.7 x 10(-12) ?(-1) cm(-1) at intensity I = 570 mW/cm(2), DAST showed a gain of 2.2 cm(-1) for an absorption of alpha = 1.8 cm(-1). With grating buildup times below 1 s at light intensities of 300 mW/cm(2), DAST is a promising candidate for photorefractive applications in the near infrared.