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1

Low-pass RC filter modified by liquid crystal exhibiting one Debye relaxation : theoretical approach

Perkowski Paweł J.

Opto-Electronics Review

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2022

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Vol. 30, No. 3

art. no. e141949

EN

The solid dielectrics used in the capacitors exhibit rather high-frequency relaxations. This means that in the radio-frequency range, the capacitors exhibit a constant capacity. When liquid crystal is put into the capacitors, it is observed that in the radio-frequency range the capacity changes (decreases with frequency). This is due to the fact that liquid crystals exhibit relaxation in the radio-frequency range. In this paper, the formulas for the electricresponse of a low-frequency RC filter with liquid crystal characterized by complex electric permittivity are derived. One Debye-type relaxation is assumed in the calculations. The influence of strengths and relaxation time (frequency) of relaxation mode in liquid crystalon the electric response of low-frequency filters is discussed.

2

Optical sensor of flavonoids based on liquid crystal

Sushynskyi Orest, Petrina Romana, Gubriy Zoriana, Khomyak Semen, Mykytyuk Zinoviy, Novikov Volodymyr

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2019

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T. 9, nr 1

61--64

EN

In order to solve the problems associated with the express registration of the presence of biologically active substances in callus biomass, we propose the use of cholesteric liquid crystal (CLC) with a spiral structure as a material of a sensitive element of optical sensor of flavonoids. Cholesteric liquid crystal BLO62 is proposed to use as a sensitive element. Spectral characteristics of alcohol solutions of flavonoids (20%, 40%, 70% and 90%) were obtained. The interaction of CLC with quercetin was analyzed. The scheme of the primary information signal converter is developed in which the current from the photodetector is transmitted to the developed signal converter. The device is implemented with the common use Atmega 328 microcontroller manufactured by Atmel. Speciality of this structural scheme is its flexibility and versatility, which makes it easy to reconfigure the parameters of the firmware for the registration of various types of investigated mediums.

PL

Aby rozwiązać problemy związane z szybką analizą obecności substancji biologicznie czynnych w biomasie kalusa, proponujemy zastosowanie materiałów ciekłokrystalicznych o spiralnej strukturze supramolekularnej jako wrażliwego elementu czujnika optycznego flawonoidów. Proponuje się stosowanie cholesterycznego ciekłego kryształu BLO62 jako wrażliwego elementu. Uzyskano charakterystykę spektralną roztworów alkoholowych flawonoidów (20%, 40%, 70% i 90%). Przeanalizowano interakcję cholesterycznego ciekłego kryształu z kwercetyną. Opracowano schemat pierwotnego przetwornika sygnału, w którym prąd z fotodetektora jest przesyłany do opracowanego przetwornika sygnałów. Urządzenie jest realizowane na bazie mikrokontrolera Atmega32 Atmega 328. Cechą tego schematu strukturalnego jest jego elastyczność i wszechstronność, co ułatwia rekonfigurację parametrów oprogramowania do rejestracji różnych typów badanych substancji.

3

Mid-wave infrared liquid crystal shutter for breathalyzer applications

Piecek W., Jaroszewicz L., Miszczyk E., Raszewski Z., Mrukiewicz M., Kula P., Jasek K., Perkowski P., Nowinowski-Kruszelnicki E., Zieliński J., Kędzierski J., Olifierczuk M., Chodorow U., Morawiak P., Mazur R., Kowiorski K., Harmata P., Herman J.

Opto-Electronics Review

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2017

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Vol. 25, No. 2

103--109

EN

There exists a problem with an in situ diagnostics of contamination of ethyl alcohol in a human being exhaled air. When ethyl alcohol in a mouth blowing (in a gaseous state) exists, the characteristic C-H stretch absorption bands in CH3 and CH2 functional groups in ethanol (CH3CH2OH) appear at a wave length of λ = 3.42 µm. To investigate the presence of ethyl alcohol in exhaled human air, the light beam of λ = 3.42 µm is passing through an air sample. If one alternately measures the intensity of the investigated beam and the reference, a percentage of ethanol in the air sample can be estimated using a sensitive nondispersive infrared (NDIR) system with a stable operating flow mass detector. To eliminate a mechanical chopper and noise generating stepper motors, a photonic chopper as a liquid crystal shutter for λ = 3.42 µm has been designed. For this purpose, an innovative infrared nematic liquid crystal mixture was intentionally prepared. The working mixture was obtained by a selective removal of C-H bonds and its exchange by heavier polar substituents, what ensures a lack of absorption band of C-H bonds. The paper presents theory, concept and final experimental results of the infrared nematic liquid crystals mixture and the liquid crystal shutter for breathalyzer applications.

4

Electrically tunable long-period fiber gratings with low-birefringence liquid crystal near the turn-around point

Czapla A., Bock W. J., Woliński T. R., Mikulic P., Dąbrowski R., Nowinowski-Kruszelnicki E.

Opto-Electronics Review

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2017

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Vol. 25, No. 4

290--295

EN

In this work, an electrically tunable long-period fiber grating (LPFG) coated with liquid crystal layer (LC) is presented. As a LC layer, a prototype low-birefringence 1550A LC mixture was chosen. As a LPFG host, two types of gratings were studied: the LPFGs based on a standard telecommunication fiber, produced by an electric arc technique with a period of 222 µm, and the LPFGs based on a boron co-doped fiber written by a UV technique with a period of 226.8 µm. The relatively short period of these gratings allowed exploiting unique sensing properties of the attenuation bands associated with modes close to the turn-around point. Experiments carried out showed that for the UV-induced LPFG with a LC layer, on the powered state the attenuation band could be offset from the attenuation band measured in the unpowered state by almost130 nm. When the arc-induced LPFG was coated with the LC, the depth of the attenuation band could be efficiently controlled by applying an external E-field. Additionally, all experimental results obtained in this work were supported by the theoretical analysis based on a model developed with Optigrating v.4.2 software.

5

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.

6

Nonlinear optimization approach to determine optical dispersion in liquid crystals

Marciniak P., Moszczyński P.

Optica Applicata

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2016

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Vol. 46, nr 4

619--628

EN

We report the method of calculating optical dispersion of selected nematic liquid crystals using maxima positions of a transmittance filled Fabry–Pérot filter. Additionally, the profiles of a dispersive phase of reflection have been calculated. The transmittance of Fabry–Pérot filter was described as a form of a modified Airy formulae (with parameters dependence on wavelength and phase of reflection). To correctly use this function, additionally the phase of reflection is defined, taking into account the problem of a beam penetrating the mirror structure. The authors of this work assume that the point where the beam is reflected is not created strictly on the boundary of media, but it is moved into the mirror structure. The depth of the penetration changes the optical way of the wave and in consequence – the optical width of the Fabry–Pérot filter cavity. The parameter describing this phenomenon was named as a phase of reflection. This work presents how to calculate: the phase of reflection, one of refractive indices of birefringent medium inside Fabry–Pérot filter and the cavity width at the same time with the use of composed nonlinear optimization methods. The proposed method is an alternative for a reverse task solution which is hard to define properly here.

7

The Relationship between the Monomer Chain Length and the Electro-Optical Properties of Polymer Dispersed Liquid Crystals

Liu J., Ozga K., Liu X., Zhen Z., Plucinski K. J., Szota M., Kityk I. V.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 1

457--460

EN

Five polymers dispersed liquid crystalline (LC) films were fabricated using photo-polymerizable monomers with different lengths of carbon chains. These LC films have shown different electro-optical (EO) properties. Through their SEM pictures, the relationship between the linear electro-optical effect and the mesh size of the polymer network was explored. With the increase of number of photo-polymerizable monomers, the mesh size of the polymer network would become larger. So the liquid crystal molecules would be easily oriented in the electric field and therefore, the threshold voltage and saturation voltage would decrease. The open state response times were also reduced and the off state response times would be extended. The DFT simulations have shown principal role of the ground state dipole moments in the observed electro-optical efficiency.

8

Efektywna metoda rozpoznawania faz ciekłokrystalicznych

Orlikowska H., Bartkiewicz S.

Aparatura Badawcza i Dydaktyczna

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2016

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T. 21, nr 3

135--140

PL

Ciekłe kryształy są szeroko badane ze względu na ich zastosowanie w wielu urządzeniach optycznych oraz jako składniki mieszanin chemicznych. Powszechnie stosowane są trzy metody identyfikacji faz ciekłokrystalicznych: obserwacja tekstur za pomocą mikroskopu polaryzacyjnego, dyfrakcja promieni rentgenowskich oraz termodynamiczna metoda współmieszalności. Wszystkie wymienione techniki mają jednak istotne ograniczenia. W tej pracy, po raz pierwszy, prezentujemy nową metodę identyfikacji mezofaz opartą na mikroskopii polaryzacyjnej – dynamiczną dwuwymiarową analizę termooptyczną (DDAT). Istota metody polega na statystycznej analizie obrazów mikroskopowych powstałych przy depolaryzacji światła przechodzącego przez medium ciekłokrystaliczne umieszczone w zmiennym polu elektrycznym. Opisana metoda jest efektywna i tania, co umożliwia zastosowanie jej zarówno w profesjonalnych badaniach, jak i w procesie dydaktycznym.

EN

Liquid crystals are widely studied because of their application in many optical devices and as components of chemical mixtures. For identifying liquid crystalline phases three basic methods are used: polarizing microscope observations of optical texture, X-ray diffraction and miscibility method. All of these techniques have significant limitations. In this work, for the first time, we present a new method to identify mesophases based on polarization microscopy – dynamic two-dimensional thermooptical analysis (DTD TOA). The essence of the method is based on a statistical analysis of microscopic images resulting from the depolarization of the light passing through the liquid crystal medium disposed in the alternating electric field. The described method is effective and inexpensive, which makes it attractive for applications in both professional research and the teaching process.

9

Molecular order and dynamics of 5CB liquid crystals in confined space - computer simulation

Gwizdała W., Gburski Z.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2015

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Vol. 19, No 1

35--64

EN

We studied the dynamical and structural properties of an important nematic 4-n-pentyl-4’-cyanobiphenyl (5CB) mesogen placed near carbon allotropes (graphene, nanotube), using modeling and molecular dynamics simulations (MD). Every investigated nanosystem (a free cluster of 5CB, a 5CB cluster confined in a single-walled carbon nanotube, 5CB mesogens located between two graphene sheets, a 5CB thin layer on a single-walled carbon nanotube, a thin layer of a 5CB molecules near graphene plane) contains a liquid crystal cluster consisting of 5CB molecules (22–98 molecules). We also performed a computer experiment for a 5CB bulk sample (196 5CB mesogens) with periodic boundary conditions. The following observables were calculated for several temperatures: mean square displacement, radial distribution function and second rank order parameter of 5CB clusters. The obtained results from MD simulations were discussed and compared with the experimental data.

10

Liquid crystal dual-mode band-pass filter with improved performance

Torrecilla J., Marcos C., Urruchi V., Sánchez-Pena J. M., Chojnowska O.

Opto-Electronics Review

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2015

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Vol. 23, No. 2

121-125

EN

Over the last twenty years, there has been a growing interest in the design of tunable devices at microwave frequencies by using liquid crystals technology. In particular, the use of liquid crystals with high dielectric anisotropy allows manufacturing voltage-controlled devices to operate in a wide frequency range. In this work the frequency response of a liquid crystal band-pass filter with dual-mode microstrip structure has been studied in depth by using a simulation software tool. A reshaping of a conventional dual-mode square patch resonator band pass filter with a square notch, studied in the literature, has been proposed with the goal of improving the filter performance. The main features achieved are a significant increase in the return loss of the filter and a narrowing of a 3-dB bandwidth. Specifically, a reduction in the filter bandwidth from 800 MHz to 600 MHz, which leads to a return loss increase from 6 dB to 12.5 dB, has been achieved. The filter centre frequency can be tuned from 4.54 GHz to 5.19 GHz.

11

Dielectric properties and molecular motions of liquid crystal molecules in 4-(2-methylbytyl) phenyl 4-(4-octylphenyl) benzoate liquid crystal having blue phase (CE8)

Otowski W., Lewińska G.

Materials Science Poland

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2015

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Vol. 33, No. 2

418--429

EN

Blue phase liquid crystals exhibit unique properties which are used in the new type of display. A blue-phase liquid crystal display was first presented commercially by Samsung in 2007. The blue-phase-three-color pixel display eliminates the need for color filters. This type of display uses blue-phase multi-component liquid crystal. Considering the one-component systems, it turns out that they are stable only in a very narrow range of temperatures between the isotropic and the chiral nematic phase (about 1 K). In 2005, a wide temperature range BP multi-component system was reported by researchers from the University of Cambridge. There are still several unsolved problems left. One of them is chemical stability and reliability. Therefore, the knowledge of molecular dynamics of blue phase liquid crystal is a prerequisite for understanding of blue-phase multi-component system. Understanding the molecular dynamics of a single component liquid-crystalline blue phase system can facilitate the solution of these problems. We present the molecular dynamics investigation of 4-(2-methylbytyl)phenyl 4-(4-octylphenyl) benzoate (CE8), which may be a good candidate to form materials suitable for blue-phase liquid crystal displays.

12

Synthesis of Conjugated Polymer Film by Electrolytic Polymerisation in Lyotropic Liquid Crystal

Eguchi H., Goto H.

International Letters of Chemistry, Physics and Astronomy

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2015

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Vol. 46

54--58

EN

We prepared lyotropic liquid crystal by using disodium cromogrycate that shows liquid crystal by dissolving in water. Next, we added monomer to the prepared solution, and electrolyic polymerisation was carried out. Finally, we obtained a conductive thin polymer film. This result shows that lyotrpic liquid crystal can be used for matrix.

13

Photo-alignment of liquid crystals in micro capillaries with point-by-point irradiation

Siarkowska A., Jóźwik M., Ertman S., Woliński T. R., Chigrinov V. G.

Opto-Electronics Review

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2014

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Vol. 22, No. 3

178-182

EN

A photo-alignment method for micro capillaries based on the SD-1 azo-dye is demonstrated. In this work a liquid-crystal molecules aligning layer is created by point-by-point irradiation of the azo-dye film by using an UV laser light. The method opens up new possibilities for an improved molecules’ orientation control in both glass- and polymer-based photonic liquid crystal fibres.

14

Intracavity polarization control in mode-locked Er-doped fibre lasers using liquid crystals

Nikodem M., Krzempek K., Zygadlo K., Dudzik G., Waz A., Abramski K., Komorowska K.

Opto-Electronics Review

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2014

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Vol. 22, No. 2

113-117

EN

In this paper we present a novel configuration of an NPR mode-locked Er-doped laser. This new optical setup uses voltage controlled LC cells to replace standard retarders (quarter- and half-waveplates) inside the laser cavity. Using this novel, mechanical-adjustment-free setup a mode-locking was obtained with sub-500 fs pulse duration and an average power exceeding 40 mW. Presented results show that using simple LC cells, an optical layout of an NPR mode-locked laser can be greatly simplified.

15

Investigation into spatial stochastization of an optical field scattered by nematic

Maksimyak P., Gavrylyak M

Optica Applicata

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2014

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Vol. 44, nr 4

555--566

EN

This paper presents the investigation results of spatial chaotization of an optical field scattered by liquid crystals during phase transition liquid–liquid crystal under an electric field. Two stochastic parameters of the field, namely, Lyapunov’s maximal index and correlation exponent were chosen for this study. It has been established that maximum variances of phase inhomogeneities of the nematic liquid crystal correspond to maximum fluctuations of an order parameter under the temperature of phase transition liquid–liquid crystal. It has been found that the analysis of the radiation field scattered during the phase transition process in the liquid–liquid crystal allows to accurately determine the phase transition temperature and voltage of forming Williams’s domains.

16

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.

17

Liquid crystal alignment in cylindrical microcapillaries

Chychłowski M., Yaroshchuk O., Kravchuk R., Woliński T.

Opto-Electronics Review

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2012

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Vol. 20, No. 1

47-52

EN

A variety of alignment configurations of liquid crystals (LCs) inside the glassy cylindrical capillaries is realized by using alignment materials providing different anchoring. The radial configuration with central disclination line is obtained for homeotropic boundary conditions. In turn, the axial, transversal and tilted alignment structures are realized by using materials for planar anchoring. The uniformity and controlling of the latter structures were provided by photoalignment method. This approach can be further used to control LC alignment in the photonic crystal fibers recognized as advanced elements for different optical devices.

18

Dielectric spectroscopy of liquid crystals : electrodes resistivity and connecting wires inductance influence on dielectric measurements

Perkowski P.

Opto-Electronics Review

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2012

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Vol. 20, No. 1

79-86

EN

Dielectric spectroscopy is a very useful experimental method for liquid crystal investigation. Electrodes made from indium tin oxide (ITO) or gold are widely used in measuring cells. During the dielectric spectroscopy measurements performed for smectic liquid crystalline mixture it was found that detection of some important relaxation modes in paraelectric SmA*, ferroelectric SmC* and antiferroelectric SmCA* phases for frequencies higher than 0.2–0.5 MHz is not possible. The measuring setup does not allow us to measure such relaxations due to its own dielectric response covering the dielectric response of liquid crystalline medium. One can observe the spurious contribution for high frequency part of the dielectric spectrum, due to non-zero resistivity of electrode material or non-zero inductivity of connecting wires. In this paper, the new model was introduced. Its final equations show how to calculate parameters of relaxations observed in liquid crystals, from dielectric response of the empty and filled measuring cell. The experimental proof of strong influence of measuring setup properties on effective (measured) values of dielectric permittivities was shown.

19

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.

20

Investigations of the materials for carbon monoxide optoelectronic sensors

Sushynskyy O., Rudyy A., Chapran M.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2012

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nr 1

18-20

EN

In this paper, experimental investigations of carbon monoxide (CO) influence on organic materials, namely the plasma of human blood, natural proteins in egg white (albumin) and liquid crystal materials, are presented.

PL

W artykule opisano eksperymentalne badania wpływu tlenku węgla (CO) na wybrane materiały organiczne: osocze ludzkiej krwi i naturalne białko jaj (albuminę), oraz materiały ciekłokrystaliczne.