Antiferroelectric liquid crystals with 45° tilt - a new class of promising electro-optic materials

Antiferroelectric liquid crystals with a tilt angle of 45 degrees have very interesting optical properties, which seem to have been overlooked so far perhaps because such materials have hardly been available. We have prepared a four-component mixture of partially fluorinated compounds with a SmC/sub n/* phase in the interval between 27.4 degrees C and 121.6 degrees C, in which the tilt angle theta saturates at 45 degrees for T<or=80 degrees C, and we investigate the optical properties, theoretically and experimentally. One of the surprising features of 45 degree materials is that they permit a remarkably high contrast by virtue of an excellent dark-state, in spite of the fact that AFLC materials are notoriously difficult to align. This is because a 45 degrees AFLC turns out to be (negatively) uniaxial instead of biaxial. We describe these properties and propose a number of potentially interesting new applications, including a polarizer-free display mode and a three-level ``phase-only'' modulator.