Rotatable liquid crystal waveplate

Abstract

A photoresist well of size 60 × 60 × 15 μm3 has been used to confine a droplet of nematic liquid crystal to create a rotatable waveplate. The optical texture of the droplet between crossed polarisers is consistent with the nematic n-director running substantially along a diameter of the droplet and connecting two nematic defects on the curved edges of the droplet. Electric field induced azimuthal rotation of the axis of the nematic liquid crystal droplet has been demonstrated. At higher temperatures, 30 °C and above, the droplet is more circular in shape and can be switched to arbitrary rotation angles. At lower temperatures, 25 °C and below, the sides of the droplet are straightened by the interaction with the well walls and the switching tends to favour discrete orientations of the optic axis. The shape of the time–voltage switching response curve for rotation by an angle of 40° also depends on the temperature of the droplet. A switching time that is inversely proportional to the voltage squared results when the droplet is nearest to circular in shape.