Prof. Dr. Heinz-Siegfried Kitzerow - Contact (Paderborn University)

Geometric-phase metalens to be used for tunable optical tweezers in microfluidics

R. Geromel, R. Rennerich, T. Zentgraf, H. Kitzerow, Liquid Crystals (2023), pp. 1-11

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Luminescent DNA-origami nano-rods dispersed in a lyotropic chromonic liquid crystal

B. Zhang, L. Nguyen, K. Martens, A. Heuer-Jungemann, J. Philipp, S. Kempter, J.O. Rädler, T. Liedl, H. Kitzerow, Liquid Crystals (2023), pp. 1-9

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Unraveling the electrochemical and spectroscopic properties of neutral and negatively charged perylene tetraethylesters

C. Wiebeler, J. Vollbrecht, A. Neuba, H. Kitzerow, S. Schumacher, Scientific Reports (2021), 11(1), 16097

Abstract

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<jats:title>Abstract</jats:title><jats:p>A detailed investigation of the energy levels of perylene-3,4,9,10-tetracarboxylic tetraethylester as a representative compound for the whole family of perylene esters was performed. It was revealed via electrochemical measurements that one oxidation and two reductions take place. The bandgaps determined via the electrochemical approach are in good agreement with the optical bandgap obtained from the absorption spectra via a Tauc plot. In addition, absorption spectra in dependence of the electrochemical potential were the basis for extensive quantum-chemical calculations of the neutral, monoanionic, and dianionic molecules. For this purpose, calculations based on density functional theory were compared with post-Hartree–Fock methods and the CAM-B3LYP functional proved to be the most reliable choice for the calculation of absorption spectra. Furthermore, spectral features found experimentally could be reproduced with vibronic calculations and allowed to understand their origins. In particular, the two lowest energy absorption bands of the anion are not caused by absorption of two distinct electronic states, which might have been expected from vertical excitation calculations, but both states exhibit a strong vibronic progression resulting in contributions to both bands.</jats:p>

All-optical switching of a dye-doped liquid crystal plasmonic metasurface

B. Atorf, H. Mühlenbernd, T. Zentgraf, H. Kitzerow, Optics Express (2020), 28(6), pp. 8898-8908

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Organic Light‐Emitting Diodes Based on a Columnar Liquid‐Crystalline Perylene Emitter

C. Keum, D. Becker, E. Archer, H. Bock, H. Kitzerow, M.C. Gather, C. Murawski, Advanced Optical Materials (2020), 8(17), 2000414

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Dynamics of a liquid crystal-based modulator with germanium substrates for mid-infrared radiation

A.M. Risse, J. Schmidtke, H. Kitzerow, Liquid Crystals (2020), 48(7), pp. 1025-1033

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DNA Origami Nano-Sheets and Nano-Rods Alter the Orientational Order in a Lyotropic Chromonic Liquid Crystal

B. Zhang, K. Martens, L. Kneer, T. Funck, L. Nguyen, R. Berger, M. Dass, S. Kempter, J. Schmidtke, T. Liedl, H. Kitzerow, Nanomaterials (2020), 10(9), 1695

Abstract

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<jats:p>Rod-like and sheet-like nano-particles made of desoxyribonucleic acid (DNA) fabricated by the DNA origami method (base sequence-controlled self-organized folding of DNA) are dispersed in a lyotropic chromonic liquid crystal made of an aqueous solution of disodium cromoglycate. The respective liquid crystalline nanodispersions are doped with a dichroic fluorescent dye and their orientational order parameter is studied by means of polarized fluorescence spectroscopy. The presence of the nano-particles is found to slightly reduce the orientational order parameter of the nematic mesophase. Nano-rods with a large length/width ratio tend to preserve the orientational order, while more compact stiff nano-rods and especially nano-sheets reduce the order parameter to a larger extent. In spite of the difference between the sizes of the DNA nano-particles and the rod-like columnar aggregates forming the liquid crystal, a similarity between the shapes of the former and the latter seems to be better compatible with the orientational order of the liquid crystal.</jats:p>

Midinfrared Birefringence of Liquid Crystals, Polarimetry, and Intensity Modulators

B. Atorf, C.H. Auf der Landwehr, R. Rennerich, H. Kitzerow, The Journal of Physical Chemistry B (2019), pp. 1384-1389

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Fabrication of Lyotropic Alignment Layers for Thermotropic Liquid Crystals Facilitated by a Polymer Template

B. Zhang, J. Schmidtke, H. Kitzerow, Advanced Optical Materials (2019), 7(8), 1801766

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Improved organic thin-film transistor performance by dielectric layer patterning

J. Temme, T. Meyers, J. Reker, F.F. Vidor, J. Vollbrecht, H. Kitzerow, J. Paradies, U. Hilleringmann, in: Fifth Conference on Sensors, MEMS, and Electro-Optic Systems, SPIE, 2019

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Pawel Pieranski – crystallographer of liquids and Alfred-Saupe-prize laureate 2019

H. Kitzerow, Liquid Crystals Today (2019), 28(1), pp. 23-30

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Curved Polar Dibenzocoronene Esters and Imides versus Their Planar Centrosymmetric Homologs: Photophysical and Optoelectronic Analysis

J. Vollbrecht, C. Wiebeler, H. Bock, S. Schumacher, H. Kitzerow, The Journal of Physical Chemistry C (2019), 123(7), pp. 4483-4492

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Switchable Plasmonic Metasurface Utilizing the Electro-Optic Kerr Effect of a Blue Phase Liquid Crystal

B. Atorf, S. Friesen, R. Rennerich, H. Mühlenbernd, T. Zentgraf, H. Kitzerow, Polymer Science, Series C (2018), 60, pp. 55-62

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Switchable Plasmonic Holograms Utilizing the Electro-Optic Effect of a Liquid-Crystal Circular Polarizer

B. Atorf, H. Rasouli, H. Mühlenbernd, B.J. Reineke, T. Zentgraf, H. Kitzerow, The Journal of Physical Chemistry C (2018), 122(8), pp. 4600-4606

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Switchable Plasmonic Metasurface Utilizing the Electro-Optic Kerr Effect of a Blue Phase Liquid Crystal

B. Atorf, S. Friesen, R. Rennerich, H. Mühlenbernd, T. Zentgraf, H. Kitzerow, Polymer Science, Series C (2018), pp. 55-62

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Liquid crystalline dithienothiophene derivatives for organic electronics

J. Vollbrecht, P. Oechsle, A. Stepen, F. Hoffmann, J. Paradies, T. Meyers, U. Hilleringmann, J. Schmidtke, H. Kitzerow, Organic Electronics (2018), pp. 266-275

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Blends of Two Perylene Derivatives: Mesogenic Properties and Application As Emitter Materials in OLEDs

J. Vollbrecht, A. Stepen, K. Nolkemper, S. Keuker-Baumann, H. Kitzerow, Polymer Science, Series C (2018), 60(1), pp. 48-54

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Two-dimensional switchable blue phase gratings manufactured by nanosphere lithography

M. Wahle, K. Brassat, J. Ebel, J. Bürger, J. Lindner, H. Kitzerow, Optics Express 25 (2017), 25(19), pp. 22608-22619

Abstract

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Switchable two dimensional liquid crystal diffraction gratings are promising can- didates in beam steering devices, multiplexers and holographic displays. For these areas of applications a high degree of integration in optical systems is much sought-after. In the context of diffraction gratings this means that the angle of diffraction should be rather high, which typically poses a problem as the fabrication of small grating periods is challenging. In this paper, we propose the use of nanosphere lithography (NSL) for the fabrication of two-dimensionally structured electrodes with a periodicity of a few micrometers. NSL is based on the self-assembly of micro- or nanometer sized spheres into monolayers. It allows for easy substrate structuring on wafer scale. The manufactured electrode is combined with a liquid crystalline polymer-stabilized blue phase, which facilitates sub-millisecond electrical switching of the diffraction efficiency at adiffractionangle of 21.4°.

Enhanced columnar mesophase range through distortions in arene cores

J. Vollbrecht, C. Wiebeler, S. Schumacher, H. Bock, H. Kitzerow, Molecular Crystals and Liquid Crystals (2017), pp. 66-73

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Liquid crystals and precious metal: from nanoparticle dispersions to functional plasmonic nanostructures

B. Atorf, T. Funck, T. Hegmann, S. Kempter, T. Liedl, K. Martens, H. Mühlenbernd, T. Zentgraf, B. Zhang, H. Kitzerow, M. Urbanski, Liquid Crystals (2017), pp. 1-19

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Ferroelectric Liquid Crystals in Microcapillaries: Observation of Different Electro-optic Switching Mechanisms

S. Knust, M. Wahle, H. Kitzerow, The Journal of Physical Chemistry B (2017), 121(19), pp. 5110-5115

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Electroluminescent and Optoelectronic Properties of OLEDs with Bay-Extended, Distorted Perylene Esters as Emitter Materials

J. Vollbrecht, S. Blazy, P. Dierks, S. Peurifoy, H. Bock, H. Kitzerow, ChemPhysChem (2017), 18(15), pp. 2024-2032

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Two-dimensional switchable blue phase gratings manufactured by nanosphere lithography

M. Wahle, K. Brassat, J. Ebel, J. Bürger, J.K.N. Lindner, H. Kitzerow, Optics Express (2017), 25(19), 22608

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Plasmonic nanostructures: spectroscopy and electron microscopy

H. Kitzerow, J. Lindner, 2017

Tunable plasmonic structures utilizing liquid crystals

B. Atorf, H. Rasouli, R. Rennerich, H. Muhlenbernd, B.J. Reineke, T. Zentgraf, H. Kitzerow, in: 2017 11th International Congress on Engineered Materials Platforms for Novel Wave Phenomena (Metamaterials), IEEE, 2017

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Liquid crystal medium and liquid crystal display

D. Wilkes, M. Wittek, A. Hoischen, H. Kitzerow, G. Nordendorf, J. Schmidtke. Liquid crystal medium and liquid crystal display, Patent EP000003124573A1. 2017.

Organic Thin-Film Transistors for AMOLED Applications

T. Meyers, J. Vollbrecht, F. Vidor, J. Reker, H. Kitzerow, U. Hilleringmann, in: IEEE Xplore, MikroSystemTechnik 2017, IEEE, 2017, pp. 1-4

Bay-Extended, Distorted Perylene Esters Showing Visible Luminescence after Ultraviolet Excitation: Photophysical and Electrochemical Analysis

J. Vollbrecht, C. Wiebeler, A. Neuba, H. Bock, S. Schumacher, H. Kitzerow, The Journal of Physical Chemistry C (2016), pp. 7839-7848

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Near infrared Kerr effect and description of field-induced phase transitions in polymer-stabilized blue phase liquid crystals

B. Atorf, H. Rasouli, G. Nordendorf, D. Wilkes, H. Kitzerow, Applied Physics Letters (2016), 108(8), 081107

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The International Liquid Crystal Society 1990–2015

D. Dunmur, H. Kitzerow, Liquid Crystals Today (2016), 25(2), pp. 24-29

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Temperature-insensitive electro-optic response of polymer-stabilized blue phases

G. Nordendorf, J. Schmidtke, D. Wilkes, H. Kitzerow, Journal of Materials Chemistry C (2016), 5(3), pp. 518-521

Abstract

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<p>Polymer-stabilized blue phase liquid crystal in-plane switching cell.</p>

Asymmetric band gap shift in electrically addressed blue phase photonic crystal fibers

M. Wahle, J. Ebel, D. Wilkes, H. Kitzerow, Optics Express (2016), 24(20), 22718

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Asymmetric band gap shift in electrically addressed blue phase photonic crystal fibers

M. Wahle, J. Ebel, D. Wilkes, H. Kitzerow, Optics Express (2016), 24(20), 22718

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Metallic and semiconducting nanoparticles in LCs

A. Sharma, M. Urbanski, T. Mori, H. Kitzerow, T. Hegmann, in: Series in Soft Condensed Matter, WORLD SCIENTIFIC, 2016

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Influence of Proton and Salt Concentration on the Chromonic Liquid Crystal Phase Diagram of Disodium Cromoglycate Solutions: Prospects and Limitations of a Host for DNA Nanostructures

B. Zhang, H. Kitzerow, The Journal of Physical Chemistry B (2016), 120(12), pp. 3250-3256

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Alignment and Graphene-Assisted Decoration of Lyotropic Chromonic Liquid Crystals Containing DNA Origami Nanostructures

K. Martens, T. Funck, S. Kempter, E. Roller, T. Liedl, B.M. Blaschke, P. Knecht, J.A. Garrido, B. Zhang, H. Kitzerow, Small (2016), 12(12), pp. 1658-1666

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Self-organized assemblies of colloidal particles obtained from an aligned chromonic liquid crystal dispersion

N. Zimmermann, G. Jünnemann-Held, P.J. Collings, H. Kitzerow, Soft Matter (2015), 11(8), pp. 1547-1553

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Chemically and thermally stable, emissive carbon dots as viable alternatives to semiconductor quantum dots for emissive nematic liquid crystal–nanoparticle mixtures with lower threshold voltage

M. Urbanski, J. Mirzaei, A. Sharma, D. Hofmann, H. Kitzerow, T. Hegmann, Liquid Crystals (2015), 43(2), pp. 183-194

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Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

M. Wahle, H. Kitzerow, Applied Physics Letters (2015), 107(20), 201114

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Electro-optic tuning of split ring resonators embedded in a liquid crystal

B. Atorf, H. Mühlenbernd, M. Muldarisnur, T. Zentgraf, H. Kitzerow, Optics Letters (2014), 39(5), 1129

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Effect of Alignment on a Liquid Crystal/Split-Ring Resonator Metasurface

B. Atorf, H. Mühlenbernd, M. Muldarisnur, T. Zentgraf, H. Kitzerow, ChemPhysChem (2014), 15(7), pp. 1470-1476

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Polycyclic Aromatic Hydrocarbons Obtained by Lateral Core Extension of Mesogenic Perylenes: Absorption and Optoelectronic Properties

J. Vollbrecht, H. Bock, C. Wiebeler, S. Schumacher, H. Kitzerow, Chemistry - A European Journal (2014), pp. 12026-12031

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Polymer-stabilized blue phases: promising mesophases for a new generation of liquid crystal displays

G. Nordendorf, A. Hoischen, J. Schmidtke, D. Wilkes, H. Kitzerow, Polymers for Advanced Technologies (2014), 25(11), pp. 1195-1207

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Columnar molecular aggregation in the aqueous solutions of disodium cromoglycate

D.M. Agra-Kooijman, G. Singh, A. Lorenz, P.J. Collings, H. Kitzerow, S. Kumar, Physical Review E (2014), 89(6), 062504

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Synthesis of Liquid Crystal Silane-Functionalized Gold Nanoparticles and Their Effects on the Optical and Electro-Optic Properties of a Structurally Related Nematic Liquid Crystal

J. Mirzaei, M. Urbanski, H. Kitzerow, T. Hegmann, ChemPhysChem (2014), 15(7), pp. 1381-1394

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Nanoparticle Doping in Nematic Liquid Crystals: Distinction between Surface and Bulk Effects by Numerical Simulations

M. Urbanski, J. Mirzaei, T. Hegmann, H. Kitzerow, ChemPhysChem (2014), 15(7), pp. 1395-1404

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Planar anchoring strength and pitch measurements in achiral and chiral chromonic liquid crystals using 90-degree twist cells

C.K. McGinn, L.I. Laderman, N. Zimmermann, H. Kitzerow, P.J. Collings, Physical Review E (2014), 88(6), 062513

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Alfred Saupe Prize 2013 Laudatio for Prof. Dr Gerd Heppke*

H. Kitzerow, Liquid Crystals Today (2014), 23(1), pp. 25-27

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Measurement of group velocity dispersion in a solid-core photonic crystal fiber filled with a nematic liquid crystal

M. Wahle, H. Kitzerow, Optics Letters (2014), 39(16), 4816

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Liquid crystal assisted optical fibres

M. Wahle, H. Kitzerow, Optics Express (2014), 22(1), 262

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Tunable infrared resonance spectra of split ring resonators embedded in a liquid crystal

B. Atorf, H. Muhlenbernd, T. Zentgraf, H. Kitzerow, in: 2013 7th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, IEEE, 2014

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Photonic Micro- and Nanostructures, Metamaterials

H. Kitzerow, in: Handbook of Liquid Crystals, Wiley-VCH, 2014, pp. 373-426

X-ray scattering of nematic liquid crystal nanodispersion with negative dielectric anisotropy [Invited]

A. Lorenz, N. Zimmermann, S. Kumar, D.R. Evans, G. Cook, M.F. Martínez, H. Kitzerow, Applied Optics (2013), 52(22), E1

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Hysteresis and memory factor of the Kerr effect in blue phases

G. Nordendorf, A. Lorenz, A. Hoischen, J. Schmidtke, H. Kitzerow, D. Wilkes, M. Wittek, Journal of Applied Physics (2013), 114(17), 173104

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Liquid crystal lasers: recent advances

J. Schmidtke, L. Lu, H. Kitzerow, E.M. Terentjev, in: SPIE Proceedings, SPIE, 2013

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Hydrophobic gold nanoparticles via silane conjugation: chemically and thermally robust nanoparticles as dopants for nematic liquid crystals

J. Mirzaei, M. Urbanski, H. Kitzerow, T. Hegmann, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences (2013), 371(1988), 20120256

Abstract

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<jats:p> We examine for the first time how chemically and thermally stable gold nanoparticles (NPs), prepared by a silane conjugation approach, affect both the thermal and the electro-optical properties of a nematic liquid crystal (LC), when doped at concentrations ranging from 0.25 to 7.5 wt%. We find that the octadecylsilane-conjugated gold NPs stabilize both the enantiotropic nematic and the monotropic smectic-A phases of the LC host with a maximum stabilization of 2 <jats:sup>°</jats:sup> C for the nematic and 3.5 <jats:sup>°</jats:sup> C for the smectic-A phases for the mixture containing 1 wt% of the silanized particles. The same mixture shows the lowest values for the Fréedericksz transition threshold voltage and the highest value for the dielectric anisotropy. Generally, all NP-containing mixtures, except mixtures with NP concentrations exceeding 5 wt%, reduce the threshold voltage, increase the dielectric anisotropy and reduce both rise and decay time; the latter particularly at temperatures at least 10 <jats:sup>°</jats:sup> C below the isotropic–nematic phase transition on cooling. </jats:p>

Microresonator-enhanced electroluminescence of an organic light emitting diode based on a columnar liquid crystal

J. Vollbrecht, O. Kasdorf, V. Quiring, H. Suche, H. Bock, H. Kitzerow, Applied Physics Letters (2013), 103(4), 043303

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Enhanced organic light-emitting diode based on a columnar liquid crystal by integration in a microresonator

O. Kasdorf, J. Vollbrecht, B. Ohms, U. Hilleringmann, H. Bock, H. Kitzerow, International Journal of Energy Research (2013), 38(4), pp. 452-458

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All-optical tunability of microdisk lasers via photo-adressable polyelectrolyte functionalization

K.A. Piegdon, M. Lexow, G. Grundmeier, H. Kitzerow, K. Pärschke, D. Mergel, D. Reuter, A.D. Wieck, C. Meier, Optics Express (2012), 20(6), 6060

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All-optical tunability of microdisk lasers via photo-adressable polyelectrolyte functionalization

K.A. Piegdon, M. Lexow, G. Grundmeier, H. Kitzerow, K. Pärschke, D. Mergel, D. Reuter, A.D. Wieck, C. Meier, Optics Express (2012), 20(6), 6060

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Kinetics of the grating formation in holographic polymer-dispersed liquid crystals: NMR measurement of diffusion coefficients

M. Tang, A. Redler, D. Topgaard, C. Schmidt, H. Kitzerow, Colloid and Polymer Science (2012), 290(8), pp. 751-755

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Doping the nematic liquid crystal 5CB with milled BaTiO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>nanoparticles

A. Lorenz, N. Zimmermann, S. Kumar, D.R. Evans, G. Cook, H. Kitzerow, Physical Review E (2012), 86(5), 051704

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Switching performance of a polymer-stabilized antiferroelectric liquid crystal based on bent-core molecules

B. Atorf, A. Hoischen, M.B. Ros, N. Gimeno, C. Tschierske, G. Dantlgraber, H. Kitzerow, Applied Physics Letters (2012), 100(22), 223301

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Electrical fine tuning of liquid crystal lasers

J. Schmidtke, G. Jünnemann, S. Keuker-Baumann, H. Kitzerow, Applied Physics Letters (2012), 101(5), 051117

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Antiferroelectric gels

J. Strauss, H. Kitzerow, Berichte der Bunsengesellschaft für physikalische Chemie (2012), 102(11), pp. 1609-1614

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Doping a Mixture of Two Smectogenic Liquid Crystals with Barium Titanate Nanoparticles

A. Lorenz, N. Zimmermann, S. Kumar, D.R. Evans, G. Cook, M. Fernández Martínez, H. Kitzerow, The Journal of Physical Chemistry B (2012), 117(3), pp. 937-941

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Three-dimensional structure in holographic polymer-dispersed liquid crystals

A. Redler, H. Kitzerow, Polymers for Advanced Technologies (2012), 24(1), pp. 7-9

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New developments in nanoparticle-liquid crystal composites: from magic-sized semiconductor nanoclusters to alignment pattern formation via nanoparticle stenciling

J. Mirzaei, R. Sawatzky, A. Sharma, M. Urbanski, K. Yu, H. Kitzerow, T. Hegmann, in: SPIE Proceedings, SPIE, 2012

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Investigations on the director field around microdisc resonators

M. Urbanski, K.A. Piegdon, C. Meier, H. Kitzerow, Liquid Crystals (2011), 38(4), pp. 475-482

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Liquid Crystal/Polymer Composites: Kinetic Study of the Grating Formation in Holographic Polymer-Dispersed Liquid Crystals

A. Redler, A. Hoischen, H. Kitzerow, Molecular Crystals and Liquid Crystals (2011), 547(1), pp. 97/[1787]-107/[1797]

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Nanocomposites of a nematic liquid crystal doped with magic-sized CdSe quantum dots

J. Mirzaei, M. Urbanski, K. Yu, H. Kitzerow, T. Hegmann, Journal of Materials Chemistry (2011), 21(34), 12710

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Electrooptic Switching in Graphene-Based Liquid Crystal Cells

M. Wahle, O. Kasdorf, H. Kitzerow, Y. Liang, X. Feng, K. Müllen, Molecular Crystals and Liquid Crystals (2011), 543(1), pp. 187/[953]-193/[959]

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Efficient electro-optic switching in a photonic liquid crystal fiber

A. Lorenz, H. Kitzerow, Applied Physics Letters (2011), 98(24), 241106

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Self-assembled quantum dots in a liquid-crystal-tunable microdisk resonator

K.A. Piegdon, M. Offer, A. Lorke, M. Urbanski, A. Hoischen, H. Kitzerow, S. Declair, J. Förstner, T. Meier, D. Reuter, A.D. Wieck, C. Meier, Physica E: Low-dimensional Systems and Nanostructures (2010), 42(10), pp. 2552-2555

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Bold relief fabrication by means of electroconvection: basic properties of a suitable mixture

M. Zöller, N. Stich, S. Benning, A. Hoischen, H. Kitzerow, Liquid Crystals (2010), 37(4), pp. 383-388

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Director field of birefringent stripes in liquid crystal/nanoparticle dispersions

M. Urbanski, B. Kinkead, T. Hegmann, H. Kitzerow, Liquid Crystals (2010), 37(9), pp. 1151-1156

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Blue Phases: Prior Art, Potential Polar Effects, Challenges

H. Kitzerow, Ferroelectrics (2010), 395(1), pp. 66-85

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Tunable photonic crystals

H. Kitzerow, Liquid Crystals Today (2010), 11(4), pp. 3-7

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33. Arbeitstagung Flüssigkristalle

H. Kitzerow, Nachrichten aus der Chemie (2010), 53(6), pp. 678-679

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Liquid Crystal Addressing by Graphene Electrodes Made from Graphene Oxide

G. Nordendorf, O. Kasdorf, H. Kitzerow, Y. Liang, X. Feng, K. Müllen, Japanese Journal of Applied Physics (2010), 49(10R), 100206

Abstract

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<jats:p> The electrooptic characteristics of the field-induced reorientation of a nematic liquid crystal are studied using graphene layers as transparent conductive electrodes. The covering of a large area with highly conductive graphene was achieved by the thermal reduction of a graphene oxide film. The conductivity of the graphene electrode provides electrooptic properties that are comparable to those of liquid crystal cells with two conventional indium tin oxide electrodes. This result confirms earlier studies and suggestions concerning graphene-based liquid crystal devices. It demonstrates that the fabrication of graphene layers via the deposition and subsequent reduction of graphene oxide is suitable for liquid crystal applications. </jats:p>

Electroconvection in nematic liquid crystals via nanoparticle doping

M. Urbanski, B. Kinkead, H. Qi, T. Hegmann, H. Kitzerow, Nanoscale (2010), 2(7), 1118

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Switchable waveguiding in two liquid-crystal-filled photonic crystal fibers

A. Lorenz, R. Schuhmann, H. Kitzerow, Applied Optics (2010), 49(20), 3846

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Alignment and electrooptic effects in nanoparticle-doped nematic liquid crystals

B. Kinkead, M. Urbanski, H. Qi, H. Kitzerow, T. Hegmann, in: SPIE Proceedings, SPIE, 2010

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Influence of a Mesogenic Dendrimer on the Morphology of Polymer–Fullerene Composites for Photovoltaics

O. Kasdorf, H. Kitzerow, J. Lenoble-Zwahlen, R. Deschenaux, Japanese Journal of Applied Physics (2010), 49(1), 01AF01

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Infiltrated photonic crystal fiber: experiments and liquid crystal scattering model

A. Lorenz, R. Schuhmann, H. Kitzerow, Optics Express (2010), 18(4), 3519

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Blue Phases: Prior Art, Potential Polar Effects, Challenges

H. Kitzerow, Ferroelectrics (2010), 395(1), pp. 66-85

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Self-assembled quantum dots in a liquid-crystal-tunable microdisk resonator

K.A. Piegdon, M. Offer, A. Lorke, M. Urbanski, A. Hoischen, H. Kitzerow, S. Declair, J. Förstner, T. Meier, D. Reuter, A.D. Wieck, C. Meier, Physica E: Low-dimensional Systems and Nanostructures (2010), 42(10), pp. 2552-2555

Abstract

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GaAs-based semiconductor microdisks with high quality whispering gallery modes (Q44000) have been fabricated.A layer of self-organized InAs quantumdots (QDs) served as a light source to feed the optical modes at room temperature. In order to achieve frequency tuning of the optical modes, the microdisk devices have been immersed in 4 – cyano – 4´-pentylbiphenyl (5CB), a liquid crystal(LC) with a nematic phase below the clearing temperature of TC≈34°C .We have studied the device performance in the temperature rangeof T=20-50°C, in order to investigate the influence of the nematic–isotropic phase transition on the optical modes. Moreover,we havea pplied an AC electric field to the device,which leads in the nematic phase to a reorientation of the anisotropic dielectric tensor of the liquid crystal.This electrical anisotropy can be used to achieve electrical tunability of the optical modes.Using the finite-difference time domain (FDTD) technique with an anisotropic material model, we are able to describe the influence of the liquid crystal qualitatively.

Tuning quantum-dot based photonic devices with liquid crystals

K.A. Piegdon, S. Declair, J. Förstner, T. Meier, H. Matthias, M. Urbanski, H. Kitzerow, D. Reuter, A.D. Wieck, A. Lorke, C. Meier, Optics Express (2010), 18(8), 7946

Abstract

Download

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Microdisks made from GaAs with embedded InAs quantum dots are immersed in the liquid crystal 4-cyano-4’-pentylbiphenyl (5CB). The quantum dots serve as emitters feeding the optical modes of the photonic cavity. By changing temperature, the liquid crystal undergoes a phase transition from the isotropic to the nematic state, which can be used as an effective tuning mechanism of the photonic modes of the cavity. In the nematic state, the uniaxial electrical anisotropy of the liquid crystal molecules can be exploited for orienting the material in an electric field, thus externally controlling the birefringence of the material. Using this effect, an electric field induced tuning of the modes is achieved. Numerical simulations using the finite-differences time-domain (FDTD) technique employing an anisotropic dielectric medium allow to understand the alignment of the liquid crystal molecules on the surface of the microdisk resonator.

2010 Piegdon,Declair,Förstner,Meier T,Matthias,Urbanski,Kitzerow,Reuter,Wieck,Lorcke,Meier C_Tuning quantum-dot based photonic devices with liquid crystals.pdf -

Photonic crystal fiber with a dual-frequency addressable liquid crystal: behavior in the visible wavelength range

A. Lorenz, H. Kitzerow, A. Schwuchow, J. Kobelke, H. Bartelt, Optics Express (2009), 16(23), 19375

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Director Fields Around Spherical and Cylindrical Micro Particles in a Liquid Crystal Host

H. Matthias, H. Kitzerow, Molecular Crystals and Liquid Crystals (2009), 508(1), pp. 127/[489]-136/[498]

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Electroconvection of liquid crystals: Tool for fabricating modulated polymer surfaces

A. Hoischen, S.A. Benning, H. Kitzerow, Journal of Applied Physics (2009), 105(1), 013540

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Blue phases come of age: a review

H. Kitzerow, in: SPIE Proceedings, SPIE, 2009

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Liquid Crystal Nano-particles, LCNANOP – a SONS II Collaborative Research Project

J.W. Goodby, M. Bates, I.M. Saez, E. Gorecka, H. Kitzerow, D. Guillon, B. Donnio, J. Serrano, R. Deschenaux, in: Mater. Res. Soc. Symp. Proc. 1134, 2009

Coupling Dynamics of Quantum Dots in a Liquid-Crystal-Tunable Microdisk Resonator

J. Förstner, C. Meier, K. Piegdon, S. Declair, A. Hoischen, M. Urbanski, T. Meier, H. Kitzerow, in: Advances in Optical Sciences Congress, OSA Technical Digest (CD) (Optical Society of America, 2009), paper NTuC2, 2009

Abstract

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We experimentally and theoretically investigate microdisk resonators with embedded quantum dots immersed in a liquid crystal in its nematic phase, showing the tunabililty of the photonic modes via external parameters like temperature or electric field.

Tunable optical properties of photonic crystals and semiconductor microdisks using liquid crystals

K.A. Piegdon, H. Matthias, C. Meier, H. Kitzerow, in: Emerging Liquid Crystal Technologies III, SPIE, 2008

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Submicrometer periodic patterns fixed by photopolymerization of dissipative structures

A. Hoischen, S.A. Benning, H. Kitzerow, Applied Physics Letters (2008), 93(13), 131903

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Influence of doping on the photorefractive properties of a polymer-dispersed liquid crystal

A. Redler, H. Kitzerow, Applied Physics Letters (2008), 93(18), 183304

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Tuning of the Optical Properties in Photonic Crystals Made of Macroporous Silicon

H. Kitzerow, H. Matthias, S.L. Schweizer, H.M. van Driel, R.B. Wehrspohn, Advances in Optical Technologies (2008), 2008, 780784

Abstract

It is well known that robust and reliable photonic crystal structures can be manufactured with very high precision by electrochemical etching of silicon wafers, which results in two- and three-dimensional photonic crystals made of macroporous silicon. However, tuning of the photonic properties is necessary in order to apply these promising structures in integrated optical devices. For this purpose, different effects have been studied, such as the infiltration with addressable dielectric liquids (liquid crystals), the utilization of Kerr-like nonlinearities of the silicon, or free-charge carrier injection by means of linear (one-photon) and nonlinear (two-photon) absorptions. The present article provides a review, critical discussion, and perspectives about state-of-the-art tuning capabilities.

An Efficient Optical Method to Detect Phase Transitions in Liquid Crystals

J. Strauß, A. Hoischen, H. Kitzerow, Molecular Crystals and Liquid Crystals (2007), 439(1), pp. 281/[2147]-291/[2157]

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Dual-Frequency Addressable Gratings Based on Polymer-Dispersed Liquid Crystals

H. Kitzerow, Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals (2007), 321(1), pp. 457-472

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