Holographic display and storage based on photo-responsive liquid crystals

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.

Liquid crystalline (LC) materials are ubiquitous in our modern life. Most of the applications where LC materials find their use depend on maintaining the orientation of the constituent LC particles. In this article, we report a recipe to control the molecular orientation. We have done a computer simulation study of a two-dimensional (2D) liquid crystalline material consisting of soft ellipses. The pair interaction is modelled by using the Gay–Berne potential. The 2D LC material is set to interact with an underlying substrate which varies periodically in one-dimension (1D) only. By controlling the substrate parameters like periodicity and strength, we showed that a nematic phase LC material transitions into different novel phases. We finally show that by applying a substrate with large periodicity, the substrate strength can be used as a control parameter to steer the LC director.

Nematic liquid crystal (LC)-based beam steering has been reported for wide applications. However, for conventional nematic LC beam steering the thickness is of several microns in order to have a wider deflection angle. The response time is relatively slow and the diffraction efficiency is low. In this work, novel beam steering based on polymer stabilized blue phase liquid crystal (PS-BPLC) has been designed and theoretically analyzed. This special mesophase of the chiral doped nematic LC has several advantageous characteristics, for example no need for alignment layers, microsecond response time and an isotropic voltage-off state. The results reveal control over phase retardation. The direction of the steered beam can be tuned by voltage. Depending on voltage configuration, either diffractive beam steering (0.5deg deviation for 1st order) or a tunable continuous phase (tunable deviation of 0.002deg) can be obtained. In the first case, the deflection angle could be tuned by stacks of samples. The second option has the same phase shift for the TE and TM modes so unpolarized light could be used. Full Text: PDF ReferencesF. Feng, I. White, T. Wilkinson, "Free Space Communications With Beam Steering a Two-Electrode Tapered Laser Diode Using Liquid-Crystal SLM", J. Lightwave Technol. 31, 2001 (2013). CrossRef E. Oton, J. Perez-Fernandez, D. Lopez-Molina, X. Quintana, J.M. Oton, M.A. Geday, "Reliability of Liquid Crystals in Space Photonics", IEEE Photonics Journal 7, 1 (2015). CrossRef J. Stockley, S. Serati, "Multi-access laser terminal using liquid crystal beam steering", IEEE in Aerospace Conference, 1972 (2005). CrossRef D. Zografopoulos and E. Kriezis, "Switchable beam steering with zenithal bistable liquid-crystal blazed gratings", Opt. Lett. 39, 5842 (2014). CrossRef Benedikt Scherger, et al., "Discrete Terahertz Beam Steering with an Electrically Controlled Liquid Crystal Device", J. Infrared. Millim. Terahertz Waves 33, 1117 (2012). CrossRef M.A. Geday, X. Quintana, E. Otón, B. Cerrolaza, D. Lopez, F. Garcia de Quiro, I. Manolis, A. Short, Proc. ICSO, Rhodes, Greece, pp. 1-4 (2010). CrossRef Y. Chen, S.-T. Wu, "The outlook for blue-phase LCDs", Proc. SPIE 9005, Advances in Display Technologies IV, 900508 (2014). CrossRef G.D. Love, A.F. Naumov, "Modal liquid crystal lenses", Liq. Cryst. Today 10, 1 (2000). CrossRef V. Urruchi, J.F. Algorri, J.M. Sánchez-Pena, M.A. Geday, X. Quintana, N. Bennis, "Lenticular Arrays Based on Liquid Crystals", Opto-Electron. Rev. 20, 38 (2012). CrossRef J.F. Algorri, G. Love, and V. Urruchi, "Modal liquid crystal array of optical elements", Opt. Express 21, 24809 (2013). CrossRef J.F. Algorri, V. Urruchi, N. Bennis, J. Sánchez-Pena, "Modal liquid crystal microaxicon array", Opt. Lett. 39, 3476 (2014). CrossRef J.F. Algorri, V. Urruchi, B. Garcia-Camara, J.M. Sánchez-Pena, "Generation of Optical Vortices by an Ideal Liquid Crystal Spiral Phase Plate", IEEE Elect. Dev. Lett. 35, 856 (2014). CrossRef D. Xu, Y. Chen, Y. Liu, S. Wu, "Refraction effect in an in-plane-switching blue phase liquid crystal cell", Opt. Express 21, 24721 (2013). CrossRef Z. Ge, S. Gauza, M. Jiao, H. Xianyu, S.T. Wu, "Electro-optics of polymer-stabilized blue phase liquid crystal displays", Appl. Phys. Lett. 94 101104 (2009). CrossRef J. Yan et al., "Extended Kerr effect of polymer-stabilized blue-phase liquid crystals", Appl. Phys. Lett. 96, 071105 (2010). CrossRef X. Wang, D. Wilson, R. Muller, P. Maker, D. Psaltis, "Liquid-crystal blazed-grating beam deflector, Appl. Opt. 39, 6545 (2000). CrossRef

A holographic memory in parallel information recording and the effect of carrier and interference noises are investigated. Noises are shown to influence the limit data storage density when information is recorded as one-dimentional holograms. A relation between the holographic memory storage capacity and the readout signal/noise ratio is determined. The use of one-dimentional holograms for interconnects in optical neural networks is considered. Another approuch for generating interconnects relies on multiplicators and beamsplitters built around special computer-synthesized HOEs. The fabrication of experimental samples of such elements for the visible spectral range by means of e-beam lithography is reported on. Combined liquid and plasmachemical development was used to provide a required relief depth. The minimum zone width is 300 nm and the maximum depth is 800 nm. Examples of beamsplitters for 630 nm and 530 nm with up to 1000 beams are given. Their possible use as auxiliary elements for making 3D holographic interconnection devices is considered.

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.

Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization-controllable optical devices, such as a holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) where the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is investigated using four types of LC composites comprised of LCs and monomers having different physical properties such as T(ni) and anisotropic refractive indices. The holographic memory formed by the LC with low anisotropic refractive index and LC diacrylate monomer implements optical reconfiguration for ORGAs at a high temperature beyond T(ni) of LC.

Particular attention has been given to updatable or dynamic holographic displays in recent years. The absence of ideal recording materials hampered the realization of their commercial applications. A lithium niobate crystal codoped with 1.0 mol. % bismuth and 6.0 mol. % magnesium has been grown with a diameter of 2-in. A moderately large saturation diffraction efficiency of 26% can be achieved, which corresponds to a refractive index change of 2.45 × 10−5. However, the photorefractive response time turns out to be only 13 ms, and the photorefractive sensitivity reaches 1.63 × 102 cm/J. This is by a factor of 104 larger than the one of congruent lithium niobate. The codoped crystal was used to demonstrate a real-time holographic display with a refresh rate of 30 Hz, which is a significant step forward for inorganic crystals in holographic display applications. Band structure calculations indicate that the dopants influence the charge distribution of the oxygen atoms which may be the clue to the origin of their excellent properties.

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.

A theoretical model and numerical results for a new kind of optical waveguide has been presented. The discussed waveguide is optically self-induced during light beam propagation along the boundary between a liquid crystal and a semiconducting polymer in an electrically driven lc cell. Experimental results obtained earlier are briefly reported here, and the theoretical model is discussed. The exploited liquid crystal was of birefringence close to 0.4. The photorefractive polymer was a poly (N-vinyl) carbazole doped with 2, 4, 7-trinitro-fluorenone. Full Text: PDF References H. Knobloch, H. Orendi, M. Buchel, T. Seki, S. Ito, W. Knoll,"Photochromic command surface induced switching of liquid crystal optical waveguide structures", J.Appl. Phys. 77, 481 (1995) [CrossRef] D.N. Christodoulides, R.I. Joseph,"Discrete self-focusing in nonlinear arrays of coupled waveguides", Opt.Lett. 13, 794 (1988) [CrossRef] A. Fratalocchi, G. Assanto, K.A. Brzdąkiewicz, M.A. Karpierz,"Discrete light propagation and self-trapping in liquid crystals", Opt. Expr. 13, 1808 (2005) [CrossRef] G. Assanto, A. Piccardi, A. Alberucci, S. Residori, U. Bortolozza,"Liquid Crystal Light Valves: a versatile platform for Nematicons", Phot. Lett. of Poland 1(4), 151 (2009) F. Sala, M. Karpierz,"Numerical simulation of beam propagation in a layer filled with chiral nematic liquid crystals", Phot. Lett. of Poland 1(4), 163 (2009) A. Spadlo, R. Dabrowski, J. Dziaduszek, S. Urban, E. Scibor, S. Gauza, S.T. Wu,"Liquid crystalline materials with high birefringence", J. Opt. Technol. 72, 659 (2005) [CrossRef] A. Walczak, E. Nowinowski-Kruszelnicki,"Polarization difference imaging system", ECLC Conference, Lisbona 2007 A. Walczak, E. Nowinowski-Kruszelnicki, Liquid Crystal Photonic Workshop, Cambridge 2008 Walczak, E. Nowinowski-Kruszelnicki,"Waveguide couplers induced optically over organic junction", Opt. Eng. 47(3) (2008) [CrossRef] N.V. Kukhtarev, S.F. Lyuksyutov, P. Buchhave, T. Kukhtareva, K. Sayano, P.P. Benerjee,"Self-enhancement of dynamic gratings in photogalvanic crystals", Phys. Rev. A 58, 4051 (1998) [CrossRef]

Holographic display has been considered as a promising display technology. Currently, low-speed generation of holograms with big holographic data is one of crucial bottlenecks for three dimensional (3D) dynamic holographic display. To solve this problem, the acceleration method computation platform is presented based on look-up table point source method. The computer generated holograms (CGHs) acquisition is sped up by offline file loading and inline calculation optimization, where a pure phase CGH with gigabyte data is encoded to record an object with 10 MB sampling data. Both numerical simulation and optical experiment demonstrate that the CGHs with 1920×1080 resolution by the proposed method can be applied to the 3D objects reconstruction with high quality successfully. It is believed that the CGHs with huge data can be generated by the proposed method with high speed for 3D dynamic holographic display in near future.

Doped liquid crystals, as super-fast refresh holographic media, are very useful in holographic 3D video display because of their extraordinarily high optical nonlinearity arising from laser-induced director axis reorientation. We obtained real-time dynamic holographic display with holographic response time under an order of a microsecond using the super-fast-response liquid crystal films. The hologram formation time and self-erasable time can both reach ~ 1 ms in this film. Holographic video display was realized using them without any cross talk between the holograms. In this paper, the mechanism of real-time hologram recording and self-erasure will be presented based on light-induced liquid crystal molecular reorientation in the films.

Quantum well lasers have attracted a great deal of attention by their many advantages such as low threshold current density, excellent temperature feature, high modulation rate and wavelength adjustability etc. The investigation on quantum well laser in mainland China started in the early 80s. AlGaAs/GaAs QW laser diode and InGaAs/GaAs strained layer QW laser diode have been developed using MBE technology with extremely low threshold current and high T0. Now the growth technologies for QW structure have been expanded to MOCVD technology. Emission wavelengths, on longer wavelength sides have been expanded up to 1.3 µm and 1.55 µm with InGaAsP/InP material system for application in optical fiber communication. On shorter wavelength sides, the emission wavelength has been expanded to lower than 670 nm, for applications in optical information processing. The characteristics of these devices will be demonstrated in this paper. The QW-DFB LD and low-dimension quantum wire and quantum dot lasers are under investigation.