Fundamental Study on Electroclinic Effect in Smectic A Liquid Crystals and the Application for Fast Optical Modulator

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In the first year of this project, we obtained the results that not only the molecular tilt but also the layer deformation are induced in the electroclinic effect.1. Using the cells whose layers are perpendicular to the glass surfaces, the X-ray diffraction experiments were carried out. The X-ray diffraction intensity was measured under an electric field as rotating the cell with the detector fixed at the Bragg angle of the inter layer spacing. With increasing the field, two peaks appeared at the symmetry positions and the separation became wide. This fact suggests that the chevron layer structure is formed by applying the field. It was confirmed that the layer tilt angle is nearly equal to the molecular tilt angle in the low field region.2. The above experiment gives information about the layer deformation perpendicular to the glass surfaces. The microscope observation, however, suggests the existence of the layer deformation parallel to the surfaces. To confirm this, it is necessary to observe the transmission Laue pattern. For this purpose, we are trying to detect the Laue pattern using the cells composed with very thin glasses. At this moment, the diffuse scattering due to the glasses prevents the observation of the Laue spot.3. Since the electroclinic effect is equivalent to the excitation of the soft mode in the paraelectric phase, we should observe the divergent increase of the dielectric constant as the temperature approaches to the phase transition point. We developed the automatic system for determining dielectric constant and confirmed the behavior.