Ferroelectric liquid crystal with sub-wavelength helix pitch as an electro-optical medium for high-speed phase spatial light modulators

Abstract

Deformed-helix ferroelectric liquid crystals (DHFLCs) with sub-wavelength helix pitch usually demonstrate sub-millisecond electro-optical response time, but they cannot provide pure phase modulation. However, here, it is shown experimentally that the planar aligned 50 μm thick layer of ferroelectric liquid crystal (FLC) mixture can be used as an electro-optical medium for the phase spatial light modulators (SLMs) if the mixture exhibits smectic C* phase (SmC*) with the helix pitch around 100 nm or less and operates in DHFLCs electro-optical mode. The electrically controlled spiral phase plate (SPP) was constructed on the base of non-chiral biphenylpyrimidines as liquid crystal smectic C matrix and trifluoromethylalkyl diester of p-terphenyldicarboxylic acid as a non-mesogenic chiral dopant. This SPP is able to form and reconfigure the vortex light fields at the frequency up to 3 kHz that was not yet achieved using known liquid crystal spatial light modulators.