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1

Dispersion of fluorescent dye in the nematic liquid crystal : enhanced photoluminescence and high birefringence

Pathak G., Agrahari K., Roy A., Srivastava A., Strzezysz O., Garbat K., Manohar R.

Opto-Electronics Review

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2018

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Vol. 26, No. 4

317--324

EN

In the present investigation optical, electro-optical and dielectric properties have been measured for nematic liquid crystal (NLC) material 1550C which is consisted of 4’-(trans, trans-4-alkylbicyclohexyl) carbonates and 4’-(4-(trans,trans-4-alkyl)-4-cyanobicyclohexane, dispersed with fluorescent dye (Benzo 2,1,3 Thiadiazole) in two different concentrations. Photoluminescence has been enhanced for dye dispersed system which is the key finding of this investigation. UV absorbance study has also been performed and found to be increased for composite system. Enhanced birefringence after dispersion of dye into pure NLC is also a prominent result of this investigation. Relative permittivity, threshold voltage and dielectric anisotropy have also been measured and found to be increased. The outcome of the present work may be very useful in the construction of liquid crystal displays (LCDs).

2

Analysis of birefringence property of three different nematic liquid crystals dispersed with TiO₂ nanoparticles

Pathak G., Katiyar R., Agrahari K., Srivastava A., Dabrowski R., Garbat K., Manohar R.

Opto-Electronics Review

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2018

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Vol. 26, No. 1

11--18

EN

In the present work TiO₂ nanoparticles (NPs) have been dispersed into three different nematic liquid crystals (2020, 1823A and 1550C) in different concentration. The value of the birefringence (Δn) has been calculated by the transmitted intensity method at a 632.8 nm wavelength. NLC 2020 used in the present study is a high birefringent material (Δn = 0.44), NLC 1550C is a low birefringent material (Δn = 0.067) and NLC 1823A is a mid birefringent material (Δn = 0.14). An increased value of birefringence has been found after dispersion of TiO₂ NPs in all three NLCs but this increment depends upon the concentration of the dopant material, temperature range and chemical character of the mixtures. It is suggested that this LC materials can be applicable in making of phase shifters, compensators and many more photonic devices.

3

Liquid-crystalline composites for point temperature measurements

Prusińska-Kurstak E., Garbat K., Kołakowska A., Kłosowicz S. J.

Biuletyn Wojskowej Akademii Technicznej

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2017

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Vol. 66, nr 2

13--24

EN

The application of cholesteric liquid crystals and composites containing them for visualization of thermal field and temperature measurement is very well known. Despite all disadvantages as limited precision and adhesion to the studied surface, this method is still of interest. In this work, we present the results of preliminary studies on polymer-dispersed cholesteric liquid crystal (PDCLC) composites designed for visualization and measurement of point temperature changes which can be used in medical diagnostics. Basing on the results of former studies, the perspective PDCLC preparation method as well as high-performance liquid-crystalline chiral nematics were obtained and applied. The microencapsulation in poly(vinyl, alcohol) has been chosen as the method of PDCLC preparation while as liquid-crystalline materials the chiral nematics were adopted.

PL

Zastosowanie cholesterycznych ciekłych kryształów i kompozytów je zawierających do wizualizacji pól cieplnych i pomiaru temperatury jest dobrze znane. Niezależnie od niedogodności, jakimi są ograniczona precyzja i adhezja do badanego podłoża, metoda ta jest ciągle interesująca. Niniejsza praca przedstawia wyniki wstępnych badań nad kompozytami typu PDCLC, zawierającymi cholesteryczne ciekłe kryształy, a przeznaczonymi do wizualizacji i pomiaru punktowych zmian temperatury, co może znaleźć zastosowanie w diagnostyce medycznej. W oparciu o wyniki poprzednich badań wytypowano i zastosowano perspektywiczną metodę otrzymywania kompozytów oraz nowe materiały ciekłokrystaliczne. Wykorzystano dyspergowanie w wodnym roztworze poli(alkoholu winylowego) ciekłokrystalicznych nematyków chiralnych.

4

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

Piecek W., Jaroszewicz L. R., Miszczyk E., Raszewski Z., Mrukiewicz M., Perkowski P., Nowinowski-Kruszelnicki E., Zieliński J., Olifierczuk M., Kędzierski J., Sun X. W., Garbat K., Kowiorski K., Morawiak P., Mazur R., Tkaczyk J.

Opto-Electronics Review

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2016

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Vol. 24, No. 4

169--182

EN

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 work piece. 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 ∆n ~0.40 at λ = 0.6328 μm, where the Mauguin limit above 5.00 ~ ∆nd >> λ/2 = 0.32 is fulfilled.

5

Chemical composition of the commerce mineral waters versus tap water in the city of Kielce

Gawdzik A., Garbat K., Gawdzik A., Gawdzik J.

Proceedings of ECOpole

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2015

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Vol. 9, No. 1

41--46

EN

Comparative analysis of the chemical composition of the commerce mineral and spring waters to tap water in the district city of Kielce has been presented in this paper. The research has been done using the latest analytical equipment which was stocked with ion chromatograph 883 Basic IC plus and spectrometer Optima 8000. The PHREEQC 2.17 program has been used in order to calculate the ion balances and SI index.

PL

W pracy porównano skład chemiczny dostępnych w handlu wybranych wód mineralnych z wodą wodociągową miasta Kielce. Badaniami objęto wody mineralne niskomineralizowane: Kroplę Beskidu, Żywiec Zdrój i Dobrowiankę; średniomineralizowane: Nałęczowiankę, Nestle Aquarel i Cisowiankę oraz wysokomineralizowane: Staropolankę 2000, Muszyniankę i Piwniczankę. Oznaczenia wykonano, posługując się najnowocześniejszym sprzętem analitycznym, tj. chromatografem jonowym 883 Basic IC plus firmy Metrohm oraz spektrometrem emisyjnym ze wzbudzeniem, w indukowanej plaźmie, Optima 8000 firmy Perkin Elmer. Bilanse jonowe oraz wartość indeksów stabilności uzyskano, wykorzystując programy Exel oraz PHREEQC 2.17.

6

Optical properties of a liquid crystal with small ordinary and extraordinary refractive indices and small optical anisotropy

Kędzierski J., Garbat K, Raszewski Z., Kojdecki M. A., Kowiorski K., Jaroszewicz L. R., Miszczyk E., Dąbrowski R., Zieliński J., Piecek W.

Opto-Electronics Review

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2014

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Vol. 22, No. 3

162-165

EN

Optical properties of a nematic liquid crystal with small refractive index and small birefringence were studied. The ordinary and extraordinary refractive indices and birefringence were measured as functions of temperature by using an Abbe refractometer and wedge nematic cells. From values of these indices the nematic orientational order parameter was calculated by using several methods and corresponding mathematical models. Kuczyński et al. method was found to be suitable for determining the order parameter also for materials featuring small ordinary refractive index, with unknown density.

7

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

Nowinowski-Kruszelnicki E., Jaroszewicz L., Raszewski Z., Soms L., Piecek W., Perkowski P., Kędzierski J., Dąbrowski R., Olifierczuk M., Garbat K., Miszczyk E.

Opto-Electronics Review

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2012

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Vol. 20, No. 4

315-322

EN

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.

8

High birefringence liquid crystal mixtures for electro-optical devices

Nowinowski-Kruszelnicki E., Kędzierski J., Raszewski Z., Jaroszewicz L., Kojdecki M., Piecek W., Perkowski P., Garbat K., Olifierczuk M., Sutkowski M., Ogrodnik K., Morowiak P., Miszczyk E.

Optica Applicata

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2012

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Vol. 42, nr 1

167--180

EN

High-birefringence nematic liquid crystals recently developed in the Military University of Technology (Poland) are examined for selected physical properties. In particular, for six liquid crystal mixtures there were determined: two components of dielectric permittivity for voltage frequencies in the range from 10 Hz to 10 MHz; rotational viscosity; splay, twist and bend elastic constants; ordinary and extraordinary refractive indices for light wavelengths in the range from 0.3 ?m to 1.6 ?m. The properties are discussed in terms of applicability of the new liquid crystals to electro-optical devices.

9

Investigation of new chiral fluorosubstituted compound exhibiting room temperature antiferroelectric phase

Czerwiec J. M., Żurowska M., Garbat K., Dąbrowski R., Marzec M., Wróbel S.

Opto-Electronics Review

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2011

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Vol. 19, No. 3

270-276

EN

Influence of the electric field upon alignment of molecules in ferro- and antiferroelectric phases has been studied for two fluoro-substituted compounds exhibiting antiferroelectric phase at room temperature. Two different relaxation processes have been revealed in the ferroelectric as well as antiferroelectric phase. Low temperature value of spontaneous polarization is ca. 130 nC/cm² for both substances studied. The substances align very well in the external electric field - a mono-domain of the ferroelectric SmC* phase can be obtained in about 3.5 hours.