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11. Chapter POLICRYPS Composite Materials: Features and Applications

Author

De Sio, L., Veltri, Alessandro, Tabiryan, Nelson V., Caputo, Roberto, Sukhov, A. V., and Umeton, C.

Subjects
Mathematics & science, bic Book Industry Communication::P Mathematics & science::PN Chemistry::PNR Physical chemistry::PNRH Electrochemistry & magnetochemistry
Abstract

Physical chemistry

Published
2011
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13. Steering cholesteric liquid crystal elastomer properties by positional variation of chiral molecular building blocks

Author

van Raak, Roel J.H., Lub, Johan, Schenning, Albertus P.H.J., Broer, Dirk J., Chien, Liang-Chy, Musevic, Igor, Tabiryan, Nelson V., Stimuli-responsive Funct. Materials & Dev., and Institute for Complex Molecular Systems

Subjects
Main chain liquid crystal elastomers, Side chain liquid crystal elastomers, Crosslinked liquid crystal elastomers, Cholesteric liquid crystals
Abstract

Crosslinked Liquid Crystal Elastomers (CrLCEs) are at the forefront of the development of optoelectronics and photonics. Over the years, a materials toolset has been developed ranging from bulk synthesised nematic monomers to dedicated smectic and chiral monomers with advanced applications such as polarisation optics, iridescent coatings, and photo-responsive mechanics. CrLCEs are often prepared through a two-step approach. First, conventional reactive liquid crystal monomers are chain-extended into (short) oligomer chains which are then crosslinked to form the elastomer network. The advantage of this approach is that it gives access to a wide range of processing methods, including conventional techniques suited for liquid crystal monomers, but also emerging processing techniques such as 3D- or roll-to-roll printing. Adding chiral molecules to a nematic oligomer forms the chiral nematic or cholesteric liquid crystal phase, well-known for its characteristic helicoidal ordering of the calamitic molecules. Currently we are interested in the effect of the position of the chiral component in relation to the elastomer network: either as part of the oligomer main chain or as a pendant group to it. In this contribution we found that the dopant position may influence the way in which the cholesteric material aligns. The main chain dopant follows behaviour previously reported in similar systems, while the side chain dopant adds more process-related complexity to the optical properties. With this work we aim to add a new design consideration to the already versatile platform of CrLCEs.

Published
2022

14. Implementing achromatic diffractive waveplate optics with thin, uniformly birefringent layers

Author

Roberts, David E., Sigley, Justin, Ouskova, Olena, Pshenichnii, Andrii, Tabiryan, Nelson V., Ruane, Garreth, Serabyn, Eugene, Roberts, David E., Sigley, Justin, Ouskova, Olena, Pshenichnii, Andrii, Tabiryan, Nelson V., Ruane, Garreth, and Serabyn, Eugene

Abstract

Vector Vortex Coronagraphs can potentially exhibit superior performance in terms of starlight rejection compared to alternative coronagraph technologies aimed at exoplanet detection. Vector Vortex Waveplates (VVWs) acting as coronagraph masks are micrometer-thin with nanometer-smooth continuous structure when fabricated using liquid crystal polymers (LCPs). LCPs allow different architectures for spectrally broadband performance. In this paper, we investigate classical, so-called Pancharatnam, architectures of a system of waveplates, applied to diffractive waveplates, particularly VVWs. These classical architectures involve multiple birefringent layers with angular offsets between each pair of adjacent layers. Along with ensuring high efficiency/contrast with simple structures, they allow manufacturing advantages due to the use of a single material with no additional internal twist angle optimization requirement, and high yield due to separate fabrication of individual films. The technological challenge of combining films with high resolution patterning is overcome by using micromechanical alignment tools which also allow exploring the effects of alignment between the films for controlling optical properties of the system of diffractive waveplates.

Published
2022

15. Azodyes for liquid crystal photoalignment in displays and diffraction optical elements

Author

Chigrinov, Vladimir, Belyaev, Victor V., Kozenkov, Vladimir M., Chausov, Denis N., Margaryan, Hakob L., Hakobyan, Nune H., Tabiryan, Nelson V., Chigrinov, Vladimir, Belyaev, Victor V., Kozenkov, Vladimir M., Chausov, Denis N., Margaryan, Hakob L., Hakobyan, Nune H., and Tabiryan, Nelson V.

Abstract

Photoalignment on azo dye films is a simple and efficient way to achieve anisotropic ordering of molecules, which is promising to achieve ultra-thin high-performance dichroic polarizers. Besides, the photoalignment technique shows a unique advantage on patterned alignment applications, and enables the realization of advanced optical elements such as liquid crystal (LC) Dammann grating, LC Fresnel lens, holographic polarizers and bifocal optical-vortex lens. © 2022 SPIE.

Published
2022

30. Study of azo dye surface command photoalignment material for photonics applications

Author

Nersisyan, Sarik R., Tabiryan, Nelson V., Steeves, Diane M., Kimball, Brian R., Chigrinov, Vladimir G., and Kwok, Hoi Sing

Subjects
Azo compounds -- Usage, Azo compounds -- Optical properties, Optics -- Research, Optics -- Methods, Astronomy, Physics
Abstract

We provide detailed quantitative characterization of sulfonic bisazodye SD1 as a photoalignment material for photonics applications. The reversibility of photoalignment was tested for transformations between planar and 90[degrees] twist orientation states in a liquid crystal (LC) cell using polarized UV light. No degradation was observed for 100 cycles of transformations. A given twist angle of the LC orientation was obtained in a single step, as well as in a sequence of gradually increasing angles. A hysteresis is revealed in the latter case for planar--twist--planar cycles. The material was used for obtaining patterned orientation of a LC polymer providing similarly good quality photoalignment for UV as well as visible light. High efficiency large area and high spatial frequency optical axis gratings (or, polarization gratings) were demonstrated on a polycarbonate substrate. We show the opportunity of obtaining photoalignment in a multilayer system with single exposure to a polarized light. Finally, we provide evidence of a positive feedback in the dynamics of photoalignment due to the orientational effect of an increasing number of aligned molecules. OCIS codes: 160.0160, 160.5335, 160.3710.

Published
2010

31. Characterization of optically imprinted polarization gratings

Author

Nersisyan, Sarik R., Tabiryan, Nelson V., Steeves, Diane M., and Kimball, Brian R.

Subjects
Polymer liquid crystals -- Usage, Diffraction gratings -- Materials, Polarizers (Light) -- Materials, Astronomy, Physics
Abstract

We provide detailed description and characterization of specifics of the imprinting technique for fabrication of large-area and high-efficiency liquid crystal polymer polarization gratings. We show that the quality of polarization gratings imprinted with linear polarized light is as high as that of gratings obtained in the holographic process, while exhibiting twice larger diffraction angle. The cycloidal polarization pattern used for imprinting is obtained from a master polarization grating, and the importance of fine tuning of its peak diffraction wavelength to the wavelength of imprinting radiation is emphasized. Tuning of the peak diffraction wavelength of imprinted polarization gratings from UV to near IR was realized with the aid of multilayer structures. Since the imprinting process does not involve a holographic setup, it is insensitive to ambient conditions and vibrations and provides an opportunity for large scale production of polarization gratings. OCIS codes: 050.1940, 050.1950.

Published
2009

32. Advances in Transparent Planar Optics: Enabling Large Aperture, Ultrathin Lenses

Author

Tabiryan, Nelson V., primary, Roberts, David E., additional, Liao, Zhi, additional, Hwang, Jeoung‐Yeon, additional, Moran, Mark, additional, Ouskova, Olena, additional, Pshenichnyi, Andrii, additional, Sigley, Justin, additional, Tabirian, Anna, additional, Vergara, Rafael, additional, De Sio, Luciano, additional, Kimball, Brian R., additional, Steeves, Diane M., additional, Slagle, Jonathan, additional, McConney, Michael E., additional, and Bunning, Timothy J., additional

Published
2021
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