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Computer calculations of refractive indices in orthoconic SmCA* : is it possible to obtain ''isotropic'' antiferroelectric liquid crystal (IAFLC)?

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Perkowski P. , Raszewski Z. , Piecek W. , Kędzierski J. , Rutkowska J. , Zieliński J. , Sun X. W.

Opto-Electronics Review

2011

tom Vol. 19, No. 1

34-39

Orthoconic antiferroelectric liquid crystals (OAFLC) are promising materials for applications. The saturated value of the tilt angle for such materials is 45°, while for ''classical'' antiferroelectric liquid crystals (AFLC) it reaches typically 30°. Homogeneously oriented slab of OAFLC, unwound by surface action of cell walls is apparently optically isotropic for the light beam at normal incidence. Such unwound structure of OAFLC one can call isotropic OAFLC (IOAFLC). Optical indicatrix of OAFLC is represented by an oblate sphere (ellipsoid of revolution) with its short axis perpendicular to cell walls. Here the question arises: ''Is it possible to create isotropic AFLC (IAFLC)? An effective refractive index of IAFLC should have the same value for the light beam propagating at each direction, hence the optical indicatrix should be a sphere. In the way of theoretical considerations we found that IAFLC can exist for twisted structure of AFLC characterized by the tilt angle as high as 54.3°. Unfortunately, such a big tilt angle is still not achievable in practice. Calculations show that AFLC can be optically isotropic when the helix is not suppressed by cell walls action.

Effect of fluorination of molecular rigid core in liquid crystal biphenyl benzoate based homologous series

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Morawiak P. , Piecek W. , Żurowska M. , Perkowski P. , Raszewski Z. , Dąbrowski R. , Czupryński K. , Sun X. W.

Opto-Electronics Review

2009

tom Vol. 17, No. 1

40-44

Liquid crystalline perfluorinated biphenyl benzoates were synthesized and investigated. A highly tilted, neat orthoconic smectic antiferroelectric phase was observed. A homologous series of compounds without and with a single fluorine atom substituted at different positions of a molecular rigid core was investigated by standard methods. Influence of fluorine substitution on physical properties of antiferroelectric smectic phase was discussed as well as influence of fluorination on molecular dipole moment orientation and its value were presented. Decrease in rotational viscosity as a result of fluorine substitution within a molecular rigid core was ascribed to changes of molecular packing.

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

67%

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.

tom Vol. 24, No. 4

169--182

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.