Jitto Titus

Single-crystal thin films of organic molecular salt may lead to a new generation of electro-optic devices

Single-crystal films of an organic molecular salt, 4-dimethylamino- N -methyl-4-stilbazolium tosylate (DAST) with exceptional optical quality are prepared by a modification of the shear method. Electro-optic modulation for light propagating perpendicular to the film is measured at 720 and 750 nm wavelengths with electric fields over the frequency range of 2 kHz to 100 MHz. A modulation depth of 80% was measured at 750 nm for a field of 4 V/μm in a 4-μm-thick film. The measured electro-optic response is flat over the frequency range used (2 kHz to 100 MHz), indicating electronic origin of the electro-optic effect. The results show that these films may lead to a new generation of electro-optic devices.

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.

Electro-optic modulation at 1.5 GHz using single-crystal film of an organic molecular salt

Electro-optic modulation using single-crystal film of an organic molecular salt with light propagating perpendicular to the film (transverse configuration) has been recently reported. In this letter, we report results of measurements at high speed (up to 1.5 GHz) using such films in the same configuration. Excellent signal-to-noise ratio has been observed even at a low applied voltage (1 V across 15 μm gap) for a 3 μm thick film. The magnitudes of the electro-optic coefficients are: r11=445 pm/V and r21=148 pm/V at 750 nm. A wide range of applications of these films are predicted.