| 1. |
- Valyukh, Iryna, 1971-, et al.
(författare)
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Characteristic functions for uniformly twisted birefringent media
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 102:6, s. 063110-1-063110-7
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Tidskriftsartikel (refereegranskat)abstract
- We present two functions for characterization of birefringent media with application to twisted nematic liquid crystal (LC) cells in the field off state. The first function is for reflective LC cells and the second is for transmissive LC cells. Based on the Stockes formalism, it is shown that these functions describe the ability of a layer of the twisted birefringent medium to change polarization of the output light and are invariant to the layer orientation. The characteristic functions are found in simple procedures and can be used for simultaneous determination of retardation, its wavelength dispersion, and twist angle, as well as for solving optimization problems.
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| 2. |
- Valyukh, Iryna, 1972-, et al.
(författare)
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Characterization of the Photo-Alignment Material SD-1/SDA-2 with Spectroscopic Ellipsometry
- 2007
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Ingår i: Proceedings of the IDW'07, Japan. ; , s. 391-394, s. 391-394, s. 391-394
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Konferensbidrag (refereegranskat)abstract
- Variable angle spectroscopic ellipsometry (VASE) is applied for investigation of the azo-dye SD-1/SD-2 which are used for photoalignment of liquid crystals. The azo-dye was spin coated on silicon substrates. Samples as prepared as well as samples illuminated with polarized UV light were studied. The measured optical constants were modelled with an ensample of the Lorentz oscillators. The results confirm the reorientation mechanism of the photo-induced order formation in the azo-dye films under the action of polarized light, and also show that there exist some photochemical processes.
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| 3. |
- Valyukh, Iryna, et al.
(författare)
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Monochromatic bistable reflective and transfiective ferroelectric LCDs
- 2005
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Ingår i: Proceedings of the 25th International Display Research Conference, Eurodisplay 2005. ; , s. 305-308
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Konferensbidrag (refereegranskat)abstract
- We study single and double polarizer monochromatic bistable reflective and transfective direct view ferroelectric liquid crystal displays (FLCDs). Three types of monochromatic displays are considered Black & White, Black & Yellow, Black & Green. Theoretical approach for finding optimal parameters of an FLCD is presented.
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| 4. |
- Valyukh, Iryna, et al.
(författare)
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Optical properties of thin films of mixed Ni-W oxide made by reactive DC magnetron sputtering
- 2011
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 519:9, s. 2914-2918
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of NixW1-x oxides with x = 0.05, 0.19, 0.43 and 0.90 were studied. Films with thicknesses in the range 125-250 nm were deposited on silicon wafers at room temperature by reactive DC magnetron co-sputtering from targets of Ni and W. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectroscopic ellipsometry (SE). XRD spectra and SEM micrographs showed that all films were amorphous and possessed a columnar structure. The ellipsometric angles psi and Delta of as-deposited films were measured by a rotating analyzer ellipsometer in the UV-visible-near infrared range (0.63-6.18 eV) and by an infrared Fourier transform rotating compensator ellipsometer in the 500-5200 cm(-1) wavenumber range. SE measurements were performed at angles of incidence of from 50 degrees to 70 degrees. Parametric models were used to extract thicknesses of the thin films and overlayers of NixW1-x oxide at different compositions, band gaps and optical constants. Features in the optical spectra of the NixW1-x oxides were compared with previous data on tungsten oxide, nickel oxide and nickel tungstate.
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| 5. |
- Valyukh, Iryna, 1972-, et al.
(författare)
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Theoretical study of the optical properties of low voltage stacked cholesteric liquid-crystal displays
- 2004
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Ingår i: Asia Display/IMID'04, South Korea. ; , s. 202-204
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Konferensbidrag (refereegranskat)abstract
- We study theoretically optical properties of thin layered stacked monochrome cholesteric liquid-crystal displays. Thin thickness of the layers (~1 µm) allows us appreciably to reduce driving voltage and use such displays in smart cards. Good selective reflection is achieved due to stacked structure. Dependence of the reflectivity of this type of displays on the quality of the layers, their thickness, and liquid crystal birefringence is investigated.
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| 6. |
- Valyukh, Iryna, et al.
(författare)
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UV-induced in-plane anisotropy in layers of mixture of the azo-dyes SD-1/SDA-2 characterized by spectroscopic ellipsometry
- 2008
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. ; , s. 1274-1277, s. 1274-1277
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Konferensbidrag (refereegranskat)abstract
- The optical properties of the azo-dyes SD-1/SDA-2, which are used for photoaligning of liquid crystals (LCs), are investigated with Variable Angle Spectroscopic Ellipsometry (VASE). Films of mixture of SD-1/SDA-2 are deposited by spin coating on silicon wafers. The estimated thickness is approximately 10 nm. To achieve photo-induced anisotropy, one of the samples is illuminated during 15 minutes with linearly polarized UV light followed by thermal stabilization during 1 hour at 150 °C. VASE measurements are performed in the wavelength range 200–1350 nm at several angles of incidence and at different sample orientations. Dielectric functions of azo-dye films without/with polarized UV light illumination were modelled using an ensemble of Lorentz oscillators. The results confirm the diffusion model proposed recently for explanation of the formation of the photo-induced order in azo-dye films under the action of polarized light. Refractive indices, their wavelength dispersion and thicknesses of films of SD-1/SDA-2 are reported here.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Valyukh, Sergiy, et al.
(författare)
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Liquid-crystal based light steering optical elements
- 2011
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Ingår i: Photonics Letters of Poland. - : Photonics Society of Poland. - 2080-2242. ; 3:2, s. 88-90
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Tidskriftsartikel (refereegranskat)abstract
- Potential abilities of active optical elements based onliquid crystals are investigated. We consider liquid crystal cells in whicha desired distribution of the liquid crystal director is achieved by a non-uniform electric field and by inhomogeneous boundary conditions. Theoptical elements built on principles of diffractive optics are discussed.
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