Maxim Minchenko

Orientational Kerr effect and phase modulation of light in deformed-helix ferroelectric liquid crystals with subwavelength pitch

We study both theoretically and experimentally the electro-optical properties of vertically aligned deformed helix ferroelectric liquid crystals (VADHFLC) with subwavelength pitch that are governed by the electrically induced optical biaxiality of the smectic helical structure. The key theoretical result is that the principal refractive indices of homogenized VADHFLC cells exhibit the quadratic nonlinearity and such behavior might be interpreted as an orientational Kerr effect caused by the electric-field-induced orientational distortions of the FLC helix. In our experiments, it has been observed that, for sufficiently weak electric fields, the magnitude of biaxiality is proportional to the square of electric field in good agreement with our theoretical results for the effective dielectric tensor of VADHFLCs. Under certain conditions, the 2π phase modulation of light, which is caused by one of the induced refractive indices, is observed without changes in ellipticity of incident light.

Enhanced orientational Kerr effect in vertically aligned deformed helix ferroelectric liquid crystals

We disclose the vertically aligned deformed helix ferroelectric liquid crystal whose Kerr constant (Kkerr≈130  nm/V2 at λ=543  nm) is around one order of magnitude higher than any other value previously reported for liquid crystalline structures. Under certain conditions, the phase modulation with ellipticity less than 0.05 over the range of continuous and hysteresis-free electric adjustment of the phase shift from zero to 2π has been obtained at subkilohertz frequency.

Phase modulation and ellipticity of the light transmitted through a smectic C* layer with short helix pitch

A chiral ferroelectric smectic C* liquid crystal (FLC) with the helix pitch p 0 = 330 nm was developed to avoid any scattering of visible light when the helix is not unwound over a certain limit. Planar cells with different FLC layer thickness (16 and 44 μm) have been assembled with helix axis parallel to the glass plates and aligned along the rubbing direction. The ellipticity of the light passing through the cells vs. the electric field was investigated, and a method for evaluating the electrically controlled birefringence via ellipticity measurements has been established. We have found that the FLC cell is an optical retardation layer driven by the electric field, the effective birefringence being proportional to the square electric field. The physical origin of the electrically controlled phase shift of the light passing through the FLC layer has been analysed.

Speckle‐noise suppression due to a single ferroelectric liquid‐crystal cell

— A novel principle and simple technique of suppressing the speckle noise in images displayed by a laser projection system is proposed. Wave coherence in a laser beam and speckles are destroyed in real time when the beam passes through a single FLC cell where spatially inhomogeneous phase light modulation takes place due to special FLC material and an electrical pulse regime.

Ferroelectric C* phase induced in a nematic liquid crystal matrix by a chiral non-mesogenic dopant

We report on a ferroelectric chiral smectic C (C*) phase obtained in a mixture of a nematic liquid crystal (NLC) and a chiral nonmesogenic dopant. The existence of C* phase was proven by calorimetric, dielectric and optical measurements, and also by X-rays analysis. The smectic C* which is obtained in such a way can flow, allowing to restore the ferroelectric liquid crystal layer structure in the electro-optical cells after action of the mechanical stress, as it happens with the cells filled with NLC. The proposed method of obtaining smectic C* material allows us to create innovative electro-optical cell combining the advantages of NLC (mechanical resilience) and smectic C* (high switching speed).

Nanocomposites Consisting of Gold Nanorods and Nematic Liquid Crystals: Optical Properties

Composites consisting of nematic liquid crystal and gold nanorods have been elaborated and investigated with a polarizing microscope. It was detected, that the nanorods form inside the oriented liquid crystal matrix their own self-assembling well-ordered structures. Nanorods ordered structures appear as a result of aligning layers action and provide defects corresponding to spatial distortion of the nematic liquid crystal director field. The defects have elongated stick-like shape with long axis perpendicular to liquid crystal director. Their size, orientation and ordering depend on the technology of the cell surface treatment, on the cell filling conditions and on the nature of liquid crystal matrix.

Permittivity of Chiral Smectics in the Broad Range from 0.1 mHz to 50 kHz: Discovery of Sub-mHz Dielectric Dispersion

Dielectric dispersion of a chiral smectic liquid crystal has been measured in the very broad frequency range from 0.1 mHz to 50 kHz. Two regions of dispersion have been recognized: the first one, from 0.1 mHz to 0.1 Hz was for the first time measured, the second one, from 100 Hz to 50 kHz, which is known as mainly due to Goldstone mode, has been confirmed.

P‐232: Ferroelectric Liquid Crystal Cell for Speckle‐Noise Suppression

A new principle and simple technique of suppressing the speckle-noise in images displayed by the laser projection system is proposed. Wave phasing in a laser beam and speckles are destroyed in real time when this beam passes through a single FLC cell where spatially inhomogeneous phase light modulation takes place due to special FLC material and electrical pulse regime.