Sub-wavelength Helix Pitch Research Articles

Ferrielectric Liquid Crystal with a Subwavelength Helix Pitch As an Electro-Optic Medium for Phase Spatial Light Modulators

Ferrielectric Liquid Crystal with a Subwavelength Helix Pitch As an Electro-Optic Medium for Phase Spatial Light Modulators

Broad temperature range ferrielectric liquid crystal as a highly sensitive quadratic electro-optical material.

A chiral smectic liquid crystal in which a ferrielectric phase with a helix pitch p0 less than 125 nm exists over a temperature range of at least from -3°C to +36°C has been developed. Such a wide temperature range (including room temperatures) of the ferrielectric phase with a subwavelength helix pitch has been achieved for the first time, to the best of our knowledge, which creates opportunities for the practical use of ferrielectric liquid crystals. A quadratic electro-optical effect caused by deformations of the helix in an electric field is observed in the ferrielectric phase, and the Kerr coefficient, which reaches almost 200 nm/V2, is significantly higher than the same coefficient for the blue phase and for the smectic C* phase, which means a higher sensitivity of the developed ferrielectric liquid crystal to the electric field. The electro-optical response time does not exceed 300μs at room temperatures for this ferrielectric liquid crystal.

Broad temperature range ferrielectric liquid crystal with subwavelength helix pitch

The ferrielectric liquid crystal (FerriLC) phase with the helix pitch po of about 100 nm was revealed in a broad temperature range from -3°C to + 35°C in a mixture containing an achiral smectic-C (SmC) biphenylpyrimidine and two non-mesogenic chiral diesters of 4,4”-terphenyl dicarboxylic acid.

Erratum: "Ferroelectric smectic C* phase with sub-wavelength helix pitch induced in a nematic liquid crystal by chiral non-mesogenic dopants" [Journal Liquid Crystals and their Application, 20 (3), 26–33 (2020) DOI: 10.18083/LCAppl.2020.3.26

Erratum: "Ferroelectric smectic C* phase with sub-wavelength helix pitch induced in a nematic liquid crystal by chiral non-mesogenic dopants" [Journal Liquid Crystals and their Application, 20 (3), 26–33 (2020) DOI: 10.18083/LCAppl.2020.3.26

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

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.

Ferroelectric Smectic C* Phase with Sub-Wavelength Helix Pitch Induced in a Nematic Liquid Crystal by Chiral Non-Mesogenic Dopants

Ferroelectric Smectic C* Phase with Sub-Wavelength Helix Pitch Induced in a Nematic Liquid Crystal by Chiral Non-Mesogenic Dopants

In-plane Switching Deformed Helix Ferroelectric Liquid Crystal Display Cells

In-plane electro-optical switching (IPS) is a natural feature of a conventional planar-aligned display cell based on the deformed helix ferroelectric liquid crystal effect (DHFLC-effect) with a sub-wavelength helix pitch, if the tilt angle is close to 40 degrees.

Electro-Optical Modulation in Planar Aligned Ferroelectric Liquid Crystals with Subwavelength Helix Pitch

Electro-Optical Modulation in Planar Aligned Ferroelectric Liquid Crystals with Subwavelength Helix Pitch

Light modulation in planar aligned short-pitch deformed-helix ferroelectric liquid crystals.

We study both experimentally and theoretically modulation of light in a planar aligned deformed-helix ferroelectric liquid crystal (DHFLC) cell with subwavelength helix pitch, which is also known as a short-pitch DHFLC. In our experiments, the azimuthal angle of the in-plane optical axis and electrically controlled parts of the principal in-plane refractive indices are measured as a function of voltage applied across the cell. Theoretical results giving the effective optical tensor of a short-pitch DHFLC expressed in terms of the smectic tilt angle and the refractive indices of the ferroelectric liquid crystal (FLC) are used to fit the experimental data. The optical anisotropy of the FLC material is found to be weakly biaxial. For both the transmissive and reflective modes, the results of fitting are applied to model the phase and amplitude modulation of light in the DHFLC cell. We demonstrate that if the thickness of the DHFLC layer is about 50μm, the detrimental effect of field-induced rotation of the in-plane optical axes on the characteristics of an axicon designed using the DHFLC spatial light modulator in the reflective mode is negligible.

The quadratic electro-optical effect in ferroelectric liquid crystal helical nanostructures: role of the driving voltage shape

ABSTRACTRecently it was shown that in deformed helix ferroelectric (DHF) structure, the electrically controlled birefringence of chiral smectic C* phase with subwavelength helix pitch ( is known to be proportional to the square of the electric field E) depends on the cell thickness and on the frequency of applied voltage, given as a Step function of the time. The purpose of the present work is to investigate whether this quadratic effect depends also on the voltage function shape, comparing the electrically controlled birefringence and the Kerr constant in DHF cells with different thickness, driven by STAIR and Step voltage functions.

The quadratic electro-optical effect in ferroelectric liquid crystal helical nanostructures: role of cell thickness and voltage frequency

ABSTRACTIt was reliably proved in recent years both theoretically and experimentally that the electrically controlled birefringence of chiral smectic C* phase with subwavelength helix pitch is proportional to the square of the electric field E. The goal of the present work is to investigate the restrictions of the quadratic effect imposed by the thickness of the smectic C* layer between two solid substrates, and by the frequency of applied voltage. It is shown that these restrictions are mainly associated with the dielectric dispersion of the Goldstone mode under various boundary conditions.

Optics of short-pitch deformed-helix ferroelectric liquid crystals: symmetries, exceptional points, and polarization-resolved angular patterns.

In order to explore electric-field-induced transformations of polarization singularities in the polarization-resolved angular (conoscopic) patterns emerging after deformed-helix ferroelectric liquid crystal (DHFLC) cells with subwavelength helix pitch, we combine the transfer matrix formalism with the results for the effective dielectric tensor of biaxial FLCs evaluated using an improved technique of averaging over distorted helical structures. Within the framework of the transfer matrix method, we deduce a number of symmetry relations and show that the symmetry axis of L lines (curves of linear polarization) is directed along the major in-plane optical axis which rotates under the action of the electric field. When the angle between this axis and the polarization plane of incident linearly polarized light is above its critical value, the C points (points of circular polarization) appear in the form of symmetrically arranged chains of densely packed star-monstar pairs. We also emphasize the role of phase singularities of a different kind and discuss the enhanced electro-optic response of DHFLCs near the exceptional point where the condition of zero-field isotropy is fulfilled.

Sensors at Your Fibre Tips: A Novel Liquid Crystal- Based Photonic Transducer for Sensing Systems

Recent advances in both nano-fabrication and nano- materials open up rich new avenues in the optical sensing area. Using nano-grid electrodes, nanometer-scale photo-alignment layers and deformed helix ferro-electric liquid crystals with a sub-wavelength helix pitch of 150 nm, we have realised a fully integrated polarisation-based photonic transducer which exhibits fast response to an applied voltage/electric field, excellent linearity and allows multiplexing using standard, low cost telecom optical fibers.

Smectic nanostructures with typical size less than the visible light wavelength: physics and electro-optics

Very short helix pitch (p 0 ~150-200nm) ferroelectric liquid crystals (FLCs) have been developed. Electro-optical cells based on these mixtures are free from selective reflection and diffraction in the visible spectral range and therefore exhibit very perfect operation in deformed helix ferroelectric (DHF) mode. Two main electro-optical modes of DHF cells with sub-wavelength helix pitch are under consideration   Full text: PDF