Deformable Helix Ferroelectric Liquid Crystal (DHFLC) devices with nanodimensionally short pitch are examined for
the purpose of applications in biomedical optical imaging. While nematic Liquid Crystal (NLC) devices have been used
in our previous research as retarders, optical filters and polarization rotators and integrated into biomedical optical
imaging systems, the current research is devoted to DHFLCs and to highlight the advantages that these devices can offer.
Ferroelectric Liquid Crystal (FLC) devices are considerably faster than Nematic LC devices, the DHFLC sub group
possesses other, more desired effects. The desired electro-optical response of the device is continuous, hysteretic-free
and insensitive to the sign of the applied voltage. This can be achieved by using the DHFLC V-shaped switching effect
which is observed when the helix pitch magnitude is shifted to nanoscale below 400nm (sub-wavelength) down to 150
nm. DHFLC cells with a sub-wavelength helix pitch have small light scattering in the visible spectral range when the
applied voltage is below the critical level of the helix unwinding. Designs, experimental results and simulations are
presented particularly for the reflectivity at oblique incidence showing some unique properties including polarization
independent modulation, faster response and surface waves excitation.
In this paper we propose a new approach to fibre optic voltage sensors via voltage-controlled Liquid Crystals (LC),
which would allow direct measurement of up to 400 kV/m electric fields at multiple points. In addition, a novel
polarization independent fibre optic sensor configuration is presented that exhibits a linear electro-optic (EO) response
to variations of the electrical field under test.
Liquid crystal (LC) cells can be used in conjunction with optical fibres to develop cheap and efficient sensors, such as
voltage sensors or hydrophones. In this paper we apply an effective tensor model to describe reflection from gold-coated
deformed-helix ferroelectric liquid crystal (DHFLC) cells. We show that, depending on the polarisation of the incident
light, it is possible to obtain a linear electro-optical response to the voltage applied to the cell. Theoretical results are
compared with experimental results yielding accurate agreement.
We describe a fibre optic hydrophone array system that could be used for underwater acoustic surveillance applications
e.g. military, counter terrorist and customs authorities in protecting ports and harbors, offshore production facilities or
coastal approaches as well as various marine applications. In this paper we propose a new approach to underwater sonar
systems using voltage-controlled Liquid Crystals (LC) and simple multiplexing method. The proposed method permits
measurements of sound under water at multiple points along an optical fibre using low cost components (LC cells),
standard single mode fibre, without complex interferometric measurement techniques, electronics or demodulation
The electric field initiates the director reorientation in the whole volume of FLC layer and eventually results in the motion of domain walls. Dynamics of the domain wall motion in helix free FLC cell is considered. The domain wall motion velocity depends on the frequency of electric field change and on the polar coefficient of anchoring energy W<sub>p</sub>. Increasing the frequency or the polar part ofthe anchoring energy (when the frequency is constant) gives rise to decrease of electrooptic response time 1/<sub>τ0.1-0.9</sub> by a factor 2-3 times. Due to this the electrooptical response time can be as small as 100 μs when the electric field is about 4V/μm. These parameters are most suitable to be used in an active matrix
display (or micro-display) with the high resolution.
3D display with a volumetric screen is developed because it composes the most realistic 3D image of 3D object or scene.
The display experimental model using a stack of light-scattering shutters based on the ferroelectric LC layer was created
for the first time. Physical mechanisms of FLC layer scattering were studied. The bistable scattering regime which is
most appropriate for practical applications was found, and the total time of scattering switching on and switching off was
less than 250μs at ± 80 V. The experiments showed that the possible number of FLC shutters in a volumetric screen of
the real time 3D display can be as high as 30-100.
The novel approach to the thresholdless hysteresis free switching is described. The key parameters for this mode are capacitance of the alignment/insulating layers and conductivity of the FLCs. The influence of the chemical structure of FLC on the performance of the V-shape mode is discussed. Utilizing this new approach, we constructed a cell with an inversion frequency around 1 kHz and the saturation voltage less than 4V.
An optical device for modulation of the intensity of unpolarized light was constructed. In comparison with other modulators, this apparatus allows to reduce the loses of energy of light and preserve its angular divergence. The switching time and contrast ratio of the modulator are 50microsecond(s) and 300, respectively.
General electrooptical properties of Deformed Helix Ferroelectric (DHF) liquid crystal effect have been analyzed. This promising effect opens the door to continuous gray scale of diode active matrix displays, the most low electric voltage amplitude in comparison with any other type of liquid crystal cells can drive DHF displays cells. On the contrary, high voltage and high frequency mode of DHF effect provides the response time about 1.5 micrometers in a very broad temperature range. The electrically controlled birefringence of DHF cells could be applied in adaptive optics.
Advances in the field of studying the electrooptics of ferroelectric liquid crystal and possibilities of their practical use are considered. Liquid crystal compositions are developed with steady bistable and multistable properties and high multiplex ability for composing and displaying blocks of both the binary and analog information in fast spatial light modulators and high resolution information displays. Liquid crystal cells are created with electrooptical response time of a few microseconds.
Modulation characteristics of the light passing through a polarizer-free electrooptical cell based on a double uniaxially oriented film of polymer dispersed ferroelectric liquid crystals (PDFLC) have been studied. Theoretical analysis is presented of the dependence of the maximum light transmission, modulation depth and contrast ratio on the angle between the orientation of PDFLC films, on their optical anisotropy and the molecular tilt angle (Theta) . Parameters under study have been measured, and the experimental results are in good agreement with the theoretical estimations.
A new principle of continuous gray scale for passively addressed FLC displays and SLM matrices is proposed. It is based on the multistability effect in C*FLC. Conditions of its exhibition are defined. Experimental results for FLC cells and the laser beam intensity attenuator are given.
The steady bistable regime in FLC layers was found using FLC compositions with its own (volume) bistability. The grayscale in such a FLC possessing high spontaneous polarization value is demonstrated and explained. The row addressing time 50 mks and multiplexivity 1200 (at optical contrast more than 20:1) are reached in FLC passive addressed matrix. Monostable FLC with 2.5 mks response time (at optical contrast not less than 50:1) can be used in fast optical light valves and active addressed matrices for SLM- spatial filters.
We call the bistabifity of ferroelectric liquid crystal (FLC) cells as the surface bistability (SB), if the dispersion part of anchoring energy is responsible for this type of bistabiity. SB was predicted theoretically  and investigated experimentally [2-4] .It was shown, that SB there exists in SSFLC cells possessing the bookshelf structure of smectic C layers  and SB there exists only in limited region of multidimensional space of cell and driving voltage parameters . Anchoring energy of FLC with solid surface for SB structures is : 102 iO erg / cm2 On the other hand there exists the volume bistability (VB), which have been observed by us recently in thick (15 mkm and more) layers of new FLC compositions .VB is a special phenomenon caused only with stereo chemical nature of the FLC composition and quite independent upon surfaces. In this work we would try: to found the physical principle for experimental measurement of an average free energy density of ferroelectrics, -to describe manifestations for both SB and VB, - to compare SB and VB from point of view their free energy parameters.
Various types of polarizer-free light modulators based on polymer dispersed ferroelectric liquid crystals are discussed. Efficiency of light-modulation has been studied for different temperatures and values of the applied voltage.
The developed principles of optimization of the molecular structure and the mixture composition of smectic C<SUP>*</SUP> ferroelectric liquid crystal (FLC) are discussed, which significantly allow us to increase the speed of the electro-optic response in planar alignment of FLS. The achieved results reveal opportunity of construction of fast spatial light modulators with multiplexing owing to bistability with the time of electrical addressing about 1 microsecond(s) .