Electroabsorption in single-crystal film of a second-order optical material

In this letter, we report results of electroabsorption and resonant electro-optic measurements in single-crystal film of 4′-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST). The electroabsorption measurement was made by recording the changes in transmission through the film as an ac field was applied along the dipole axis. The electro-optic measurement was made using the field-induced birefringence method. The measurements were made in the absorptive domain, at 633 and 488nm. The modulation (ΔT∕T) due to electroabsorption decreased as the angle between the incident polarization and the dipole axis was increased. The observed electroabsorption is due to the imaginary part of the electro-optic coefficient. The real part of the electro-optic coefficient (r11) as measured at 633nm is 770pm∕V. The imaginary parts of the electro-optic coefficients at 633 and 488nm are 104 and 259pm∕V, respectively.