Theoretical approach of a polymer stabilized blue phase beam steering

A multi-angle director model is proposed to simulate and interpret the electro-optical characteristics of a blue-phase liquid crystal (BPLC) cell driven by vertical and horizontal electric fields. Instead of employing the Kerr effect, the BPLC cell is considered as a stack of several high-pretilt nematic liquid crystal layers that can be simulated using the director model. Simulations are performed based on the director model and results are compared with those obtained with Kerr-effect-based methods. The theoretical model successfully simulated the electro-optical characteristics of the BPLC, consistent with experimental data. Hence, the model is expected to aid the design of next-generation BPLC displays.

Blue phase liquid crystals (BPLCs) are self-assembled 3D photonic crystals exhibiting high susceptibility to external stimuli. Two methods for the photonic bandgap tuning of BPs were demonstrated in this work. Introducing a chiral azobenzene into a cholesteric liquid crystal could formulate a photoresponsive BPLC. Under violet irradiation, the azo dye experiences trans-cis isomerization, which leads to lattice swelling as well as phase transition in different stages of the process. Ultrawide reversible tuning of the BP photonic bandgap from ultraviolet to near infrared has been achieved. The tuning is reversible and nonvolatile. We will then demonstract the electric field-induced bandgap tuning in polymer-stabilized BPLCs. Under different BPLCs material preparation conditions, both red-shift and broadening of the photonic bandgaps have been achieved respectively. The stop band can be shifted over 100 nm. The bandwidth can be expanded from ~ 30 nm to ~ 250 nm covering nearly the full visible range. It is believed that the developed approaches could strongly promote the use of BPLC in photonic applications.

Thermal, Density, Lattice Distortion Optical Nonlinearities in Nematic, Cholesteric, and Blue‐phase Liquid Crystals

Blue phase liquid crystal display (BPLCD) is emerging as next-generation display, because of its fast response speed and very wide viewing angle. However, it has some weak points to be improved. The light leakage at the dark state affects the contrast ratio, and needs to be analyzed and improved. Considering the double-twist structure of blue phase liquid crystal (BPLC) and the simple twist structure of cholesteric liquid crystal (ChLC), the two twist structures are similar. The transmittances and reflectances of planar and focal conic texture of cholesteric liquid crystal and blue phase II liquid crystal are simulated by finite-difference time domain (FDTD) method. The FDTD method is based on the Maxwell’s equation, and can calculate the optical rotatory power directly. The effective optical rotatory powers of the three liquid crystal states are proposed and compared using the light leakages at the cell with crossed and parallel polarizers. The results show that the transmittance of BPLC with crossed polarizers is lower than that of planar texture and larger than that of focal conic texture of ChLC. The optical rotation of BPLC is not the same at any point in one periodic cross section in the light path because the liquid crystal arrangement is complex, the effective optical rotatory power is defined as the average value of the optical rotatory powers at all points. Comparing with the optical rotatory powers of planar and focal conic textures of ChLC, the optical rotatory power of BPLC is less than that of planar texture and larger than that of focal conic texture. Moreover, the Bragg reflections are also simulated, the results show that blue phase liquid crystal is similar to planar state cholesteric liquid crystal, only the reflection intensity is smaller, and no obvious Bragg reflection appears in focal conic state cholesteric liquid crystal. Considering the optical rotation and Bragg reflection, the light leakage and reflective light of BPLCD cannot be ignored if the helix pitch is not less enough, however, these of focal conic texture of ChLC are very small compared with those of BPLC, as a result, the focal conic texture of ChLC can replace blue phase liquid crystal to obtain the good dark state and high contrast ratio.

Quantitative evaluation of a coupling coefficient between the blue phase (BP) liquid crystal (LC) and the diacrylate-type polymer, which is to be either the framework or the defect line of the polymer-stabilized (PS) BPLC, is an important subject. As a coupling coefficient, the polar anchoring strength Wd between the BPLC and the diacrylate-type polymer prepared inside a thin hybrid alignment nematic (HAN) cell was evaluated by means of oblique incidence transmission spectroscopic ellipsometry. As an example, the polar anchoring strength Wd = 1.87 ×10-4 J/m2 is measured at the interface between host BPLC material with the diacrylate-type polymer performing vertical alignment (VA).

In this paper we propose a new approach to fiber optic voltage sensors via voltage-controlled Liquid Crystals (LC), which would allow direct measurement of up to 400 kV/m electric fields at multiple points. In addition, the electro-optical behavior of deformed helix ferroelectric (DHF) liquid crystal in reflective mode is described and tested. The electrically controlled reflectance has been measured at sub-kilohertz driving voltage frequency for different polarizations of the incident light. Full Text: PDF References Y.V. Izdebskaya, V.G. Shvedov, A.S. Desyatnikov, W. Krolikowski and Y.S. Kivshar, "Soliton bending and routing induced by interaction with curved surfaces in nematic liquid crystals", Opt. Lett. 35, 1692-1694 (2010). CrossRef Z. Ge, S. Gauza, M. Jiao, H. Xianyu and S.T. Wu, "Electro-optics of polymer-stabilized blue phase liquid crystal displays", Appl. Phys. Lett. 94, 101104 (2009). CrossRef Z. Brodzeli, F. Ladouceur, L. Silvestri, A. Michie, V. Chigrinov, G. Q. Guo, E. P. Pozhidaev and A. D. Kiselev, "Liquid crystal-based hydrophone arrays", APOS (2012). CrossRef T. Tanigawa, Y. Sakakibara, S. Fang, T. Sekikawa and M. Yamashita, "Spatial light modulator of 648 pixels with liquid crystal transparent from ultraviolet to near-infrared and its chirp compensation application", Opt. Lett. 34, 1696-1698 (2009). CrossRef K. H. Yang and T. C. Chieu, "Transport Properties of Ions in Ferroelectric Liquid Crystal Cells", Jpn. J. Appl. Phys. 28, 2240-2246 (1989) CrossRef I.C. Khoo and S.T. Wu, "Optics and Nonlinear Optics of Liquid Crystals", World Scientific, Singapore (1993). V.G. Chigrinov, "Liquid Crystal Devices: Physics and Applications", Artech House, Boston: London, (1999). A.D. Kiselev, E.P. Pozhidaev, V.G. Chigrinov and H.S. Kwok, "Polarization-gratings approach to deformed-helix ferroelectric liquid crystals with subwavelength pitch", Phys. Rev. E 83, 31703 (2011). CrossRef N. A. Clark and S. T. Lagerwall, "Submicrosecond bistable electro-optic switching in liquid crystals", Appl. Phys. Lett. 36, 899-901 (1980). CrossRef L.A. Beresnev, V.G. Chigrinov, D.I. Dergachev, E.P. Pozhidaev, J. Funfshilling and M. Schadt, "Deformed helix ferroelectric liquid crystal display: A new electrooptic mode in ferroelectric chiral smectic C liquid crystals", Liq. Cryst. 5, 1171-1177 (1989). CrossRef Z. Brodzeli, H.K. Bal, V.G. Chigrinov, A. Murauski, and F. Ladouceur, "Electrical energy harvesting device for current/voltage fibre-based sensors", Optical Fibre Technology (ACOFT), 2010 35th Australian Conference on Fibre Technology, 1-2, (2010). DirectLink X. Zhao, F. Boussaid, A. Bermak and V.G. Chigrinov, "High-resolution thin ?guest-host? micropolarizer arrays for visible imaging polarimetry", Opt. Exp. 19, 5565-5573 (2011). CrossRef X.H. Li, A. Murauski, A. Muravsky, P.Z. Xu, H.L. Cheung, and V. Chigrinov, "Grayscale Generation and Stabilization in Ferroelectric Liquid Crystal Display," J. Display Technol. 3, 273-279 (2007). CrossRef E.P. Pozhidaev, S. Torgova, M. Minchenko, C. Yednak, A. Strigazzi and E. Miraldi, "Phase modulation and ellipticity of the light transmitted through a smectic C* layer with short helix pitch", Liq. Cryst. 37, 1067-1081, (2010). CrossRef E.P. Pozhidaev and V.G. Chigrinov, "Bistable and multistable states in ferroelectric liquid crystals", Crystallography Reports. 51, 1030-1040 (2006). CrossRef Q. Guo, F. Fan, T. Du, and V.G. Chigrinov, "Electrooptic Response of FLC: Effect of Alignment Materials", SID'11 Conference, P-144, Los Angeles, USA, May, (2011). CrossRef G. Hegde, P. Xu, E.P. Pozhidaev, V.G. Chigrinov, and H.S. Kwok, "Electrically controlled birefringence colours in deformed helix ferroelectric liquid crystals", Liq. Cryst. 35, 1137-1144 (2008). CrossRef

We propose a new electrode design for polarization-independent cylindrical lens using a polymer-stabilized blue phase liquid crystal (BPLC). The top electrode is coated with a transparent and resistive film to generate linearly varying electric potential from center to edge; while the bottom iridium tin oxide electrode has a constant potential. Therefore, the vertical electric field across the BPLC layer varies linearly over the lens aperture and a desired parabolic phase profile is obtained automatically according to the Kerr effect. Simulation results show that this simple device is polarization independent and it has parabolic-like phase profile in a large tuning range.

Because of their non-diffraction and freely acceleration during propagation, finite energy Airy beams are interesting for application such as optical manipulation, plasma channel generation and optical vortex generation. Especially interesting are tunable/switchable Airy beams, in which the Airy beam tuning by electric field, temperature or optical intensity can be realized. Here we experimentally demonstrate polarization-independent, electrically tunable/switchable Airy beam based on polymer-stabilized blue phase liquid crystals with wide working temperature range and fast response time through a structure called vertical field driven mode.

We proposed the use of polymer‐stabilized blue phase liquid crystal (PS‐BPLC) as an optical‐see‐through combiner for augmented reality applications. The PS‐BPLC film has good polarization selectivity and wavelength selectivity, and thus could achieve high reflectance for virtual image light and high transparency for the real‐world.

We report a polymer-stabilized blue phase liquid crystal (BPLC) whose Kerr constant is about 2.2× larger than previous record. When filled in a 3.2-μm-thick vertical field switching cell, the on-state voltage is merely 8.4 V (at λ = 514 nm) while keeping submillisecond response time and negligible hysteresis (<1%) at the room temperature. These results imply that the dawn of BPLC era for high speed display and photonic devices has finally arrived.

We have demonstrated polymer dispersed blue phase (PDBP) liquid crystal films by encapsulating blue phase liquid crystal in a matrix of polymer. The phase‐separated blue phase liquid crystal molecules show droplets with a small size distribution and exhibit a blue phase at room temperature. The PDBP films enable field‐induced birefringence at low switching voltage. Details of preparation of PDBP and their thermal, optical and electro‐optical properties will be presented.

We describe the underlying theories and experimental demonstrations of passive temperature stabilization of silicon photonic devices clad in nematic liquid crystal mixtures, and active optical tuning of silicon photonic resonant structures combined with dye-doped nematic and blue phase liquid crystals. We show how modifications to the resonator device geometry allow for not only enhanced tuning of the resonator response, but also aid in achieving complete athermal operations of silicon photonic circuits. [Ref.: I.C. Khoo, DC-field-assisted grating formation and nonlinear diffractions in methyl-red dye-doped blue phase liquid crystals, Opt. Lett. 40, 60-63 (2015); J. Ptasinski, I.C. Khoo, and Y. Fainman, Enhanced optical tuning of modified-geometry resonators clad in blue phase liquid crystals, Opt. Lett. 39, 5435-5438 (2014); J. Ptasinski, I.C. Khoo, and Y. Fainman, Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals, Materials 7(3), 2229-2241 (2014)].

In this paper, a stable twist grain boundary A (TGBA*) and blue phase liquid crystal (LC) blend is prepared by mixing an achiral-imine-type compound with cholesteryl pelargonate and 4-cyano-4’-pentylbiphenyl (nematic LC). The LC blend has five LC phases, which contain the TGBA* phase at room temperature and the blue phase as frustrated LC.

Hysteresis-free polymer-stabilised blue phase liquid crystals comprising low surface tension monomers

A polymer-stabilized blue phase liquid crystal is one of the candidates for the next-generation display material. In this study, effects of monomer/liquid crystal compositions on electro-optical characteristics of polymer-stabilized blue phase liquid crystals were investigated. By optimizing monomer/liquid crystal compositions, lower operating voltage, reduction in hysteresis and residual birefringence were achieved. However, some technical issues remain to be overcome.