Edward Nowinowski-Kruszelnicki

The Origin of High Optical Tilt in a Homologous Series of Fluorinated Antiferroelectric Liquid Crystals

The compounds from the fluorinated nF6B (n = 1,2,3,4,5,6,7) homologous series were investigated by means of optical, electrooptical, refractometrical, dielectric, densytometric, X-ray and IR spectroscopy methods. For some compounds being a subject of investigations a computer simulation of molecular properties were done. In our opinion high value of optical tilt Θo angle in comparison with a tilt angle obtained from X-ray measurements can be interpreted in terms of de Vries model of SmA* phases as well as of dimers creation process.

On the Importance of the Molecular Core Interactions on the Induction of the High Optical Tilt Angle

Two smectogens being structural analogs with the opposite space orientation of the COO ester group in the molecular core exhibit extremely different tilt angles. A molecular mechanism of the induction of the high optical tilt angle is searched on the basis of extensive investigations of those compounds. Computer modeling of molecules and investigations of physical parameters of smectic phases were done. Different molecular aggregates forming smectic phases were observed. The size and shape of those aggregates are estimated on the basis of measurements and calculations. The different values of the tilt angles in studied compounds were discussed.

Liquid crystal cell for space-borne laser rangefinder to space mission applications

Liquid crystal cell (LCC) for space-borne laser rangefinder to space mission applications was developed, manufactured and tested under cooperation between Military University of Technology (MUT) in Poland and Vavilov State Optical Institute (Vavilov SOI) in Russia. LCC operates in twisted nematic mode, commutating the polarization plane of a laser beam working at 1.064 μm and the energy density not smaller than 0,15 J/cm2 at the pulse duration about 8 ns. The transmission of LCC is not smaller than 95% at the aperture diameter not less than 15 mm. Switching on and switching off times in a 2.5-μm thick LCC driven by voltage of 10 V are not larger than 0.7 ms and 7 ms, respectively, in the operating temperature range from 20°C to 40°C. The LCCs developed in MUT were positively tested under space requirements in Vavilov SOI.

Dielectric properties of highly anisotropic nematic liquid crystals for tunable microwave components

In this Letter, we report on measurements of the complex permittivity of highly anisotropic nematic liquid crystals at microwave frequencies as a function of the AC bias voltage. Permittivity measurements have been performed by the split post dielectric resonator technique. The experiments have shown that when the AC bias voltage increases from 0 to 8 V, the real part of the permittivity of these liquid crystals changes by up to 28%. The tunability and the relatively low dielectric losses observed in these liquid crystal mixtures mean that they are ideal materials for the design of tunable microwave components.

Measurement of elastic constants of nematic liquid crystals with use of hybrid in-plane-switched cell

A new method for quick and pretty accurate measurements of splay, twist and bend elastic constants of nematic liquid crystals is experimentally verified. The main concept relies on exploiting only the electric field and determining magnitudes of nematic elastic constants from threshold fields for Freedericksz transitions in only one hybrid in-plane-switched cell. In such cell the deformations of an investigated liquid crystal are controlled by three separated pairs of electrodes confining measurement domains. In two of them inter-digital electrodes are mounted on one cell cover. Splay, twist and bend elastic constants can be measured by a proper choice of electrodes’ configuration together with orienting cover coatings (without applying magnetic fields). In this paper, we describe layout of our cells and results of experimental tests by using different liquid crystals: 5CB and 6CHBT (with positive dielectric anisotropy), Demus’ esters (with negative dielectric anisotropy) and new liquid crystals mixtures produced in our university.

Transparent laser damage resistant nematic liquid crystal cell “LCNP3”

There exists the problem in diagnostics of dense plasma (so-called Thomson diagnostics). For this purpose the plasma is illuminated by series of high energy laser pulses. The energy of each separate pulse is as large as 3 J, so it is impossible to generate a burst of such pulses by a single laser. In this situation, the pulses are generated by several independent lasers operating sequentially, and these pulses are to be directed along the same optical path. To form an optical path with λ = 1.064 μm and absolute value of the laser pulse energy of 3 J, a special refractive index matched twisted Nematic Liquid Crystal Cell of type LCNP3, with switching on time τON smaller than 3 μs was applied.

Microwave complex permittivity of voltage-tunable nematic liquid crystals measured in high resistivity silicon transducers

A split post dielectric resonator is used to determine the effect of AC bias voltage on the microwave complex permittivity of nematic liquid crystals. High resistivity silicon transducers separated by 100 μm are bridged by nematic liquid crystals and their properties determined. The in-plane permittivity of liquid crystals can be effectively tuned (change of effective permittivity of up to 8%) by increasing the AC bias voltage from 0 to 6 V. Using high resistivity silicon allowed us to obtain tunable dielectric stacks with relatively small dielectric losses at microwave frequencies.

Liquid Crystal Elements of Laser Optics. The Optical Isolator

Abstract The studies have been done on the possibility of liquid crystals application for the optical isolation of laser systems. Tie appropriate elements containing different mesogenic materials have been made. The results suggest that these elements are very useful in laser systems.

Refractive index matched half-wave plate with a nematic liquid crystal for three-dimensional laser metrology applications

Abstract There exists a need in a quality and accuracy of a three-dimensional laser metrology operating in numerically controlled automatic machines. For this purpose, one sends three laser beams mutually perpendicular. These three beams of the wavelength λ = 0.6328 μm are generated by the same laser and are directed along three independent, orthogonal, mutually perpendicular, optical paths with a given light polarization plain. Using these beams, constituting the frame of coordinates, three independent laser rangefinders are able to determine spatial coordinates of a working tool or a workpiece. To form these optical pulses, a special refractive index matched Half-Wave Plate with nematic Liquid Crystal (LCHWP) was applied. The presented half-wave plate is based on a single Twisted Nematic (TN) cell (with the twist angle Φ = π/2) of a rather high cell gap d ~15 μm filled with a newly developed High-Birefringence Nematic Liquid Crystal Mixture (HBLCM) of optical anisotropy as high as Δn ~0.40 at λ = 0.6328 μm, where the Mauguin limit above 5.00 ~ Δnd >> λ/2 = 0.32 is fulfilled.

Large LC Droplets in Polymer Matrix

The methods of preparation of PDLC containing liquid crystals droplets of size larger than 15 μm in planar cells are presented. The morphology of such systems is discussed. The essential properties of electro-optical switching in large LC droplets are presented. The possibility of an application of such systems to measure elastic properties of confined LC is shown.