This PDF file contains the front matter associated with SPIE Proceedings Volume 11708, including the Title Page, Copyright information and Table of Contents

A driving torque origin of Smectic Single Domain (SSD) liquid crystals are discussed. SSD liquid crystals provide sub-millisecond response time both at rise and decay processes, respectively with applied electric field polarity dependent switching. Some empirical approaches revealed the driving torque is highly dependent on SSD liquid crystal molecular stacking configurations. A uniformly stacked SSD liquid crystal panel showed in-plane only retardation switching and a non-uniformly stacked panel showed mixing between in-plane and out-of-plane retardation switching. A driving torque origin of an SSD liquid crystal panel is discussed based on analysis of empirical investigations.

General liquid crystal (LC) materials have considerably large birefringence in wide frequency regions in the electromagnetic wave spectra, extending to the THz, millimeter wave (MMW), and microwave. LC materials can potentially be applied to some excellent control devices in novel frequency regions as display devices in optics regions. However, the birefringence of LC materials synthesized for display applications generally decreases by approximately half in the MMW region. Furthermore, the small remaining absorption loss in the MMW region must lead to a fatal device loss, as the LC layer becomes extremely large in the application field. New LC materials beyond the display application have been desired in novel LC application fields. In this work, a new class of LC materials consisting of hydrogen bonding is evaluated in the MMW region for the first time. Some optical properties different from those of conventional LC materials are discovered. The most distinct property is that the birefringence of the hydrogen-bonded LC materials in the MMW region becomes considerably larger than that in visible rays, which is totally inversion in relation with conventional LC materials. The absorption coefficients are as small as those of the best LC materials developed for microwave applications. Although some disadvantages are associated with the application of actual devices in this stage, the distinct dispersion properties make a breakthrough imminent in this application fields.

Amongst many research applications, liquid crystal on Silicon spatial light modulators (LCoS SLM) are used in telecommunication applications as a beam steering device. The efficiency of the device is determined by the reflectivity of its backplane and the efficiency of the addressed phase function. While a dielectric mirror coating (DMC) helps improve the reflectivity, fringing field effects are also enhanced, leading to a decrease in diffraction efficiency. To minimize the thickness of the dielectric mirror, properly identifying the relevant parameter, which has an impact on the reflectivity of the backplane, is important. From experiment results and simulation results from the finite element method, we found the pixel shape as the relevant parameter. With the pixel shape taken into consideration, we show an example of optimized DMC.

An architecture for a wide angle-of-view (AOV) liquid-crystal based digital-neutral-density (DND) filter is proposed and analyzed. The DND filter is a unique arrangement of liquid crystal display materials which shows promise for use at the input of ultra-wide-angle image capture lenses. Relevant platforms include drones, action video cameras, DSLRs, and broadcast/cinema cameras.

We introduce a twisted-nematic LC cell, which can rotate the polarization angle of the polychromatic light. We used interdigitated electrodes to apply an in-plane field to control the twist angle. Thanks to the asymmetrical anchoring in the LC cell, the twist angle could be rotated continuously by increasing the applied electric field. The linearly polarized light incident on the LC cell can be rotated following the twist direction. Since it does not require an additional retardation film such as QWP, there is no degradation of the performance at a specific wavelength even for the polychromatic light.

Switchable optical elements incorporating polymer structure and a liquid crystal material offer devices with a voltage controlled phase difference at low cost. The polymer structure may be fabricated using established replication techniques. Earlier work has demonstrated such devices with good optical quality and high diffraction efficiencies but with geometric restrictions due to the formation of defects within the device in some situations. Earlier work used surface forces from an aligning surface to establish the director orientation of the liquid crystal. In this work improved control of the director is achieved through the use of a liquid crystal material exhibiting a reversal of the dielectric anisotropy at different driving frequencies. Such a material allows the director to be actively driven either towards homeotropic or planar alignment depending upon the frequency of the drive waveform. Use of a liquid crystal material with a dielectric anisotropy inversion has the advantage in this case that the liquid crystal orientation is less dependent upon surface forces.

Surface photoalignment has been utilized to control the liquid crystalline (LC) orientation by exposing the photosensitive surface coatings to linearly polarized light. However, there are limitations in cell thickness and director orientation complexity if surface photoalignment was conducted. An alternative approach in controlling the director orientation is bulk photoalignment. Azobenzenes, which have been used for surface photoalignment due to fast reorientation during exposure, are homogeneously mixed into a nematic LC. We present results on how azobenzene doped LCs can be aligned in various standard orientations. In addition, rewriting alignment and patterning complex director orientations via bulk alignment will be discussed.

We present a facile method to control the three-dimensional (3D) orientation of blue phase (BP) liquid crystals. The field-induced intermediate phases, focal conic and BP X, from electrically unwound homeotropic state induce the [001] crystal axis to be aligned along the surface anchoring and the (110) crystal plane oriented parallel to the substrate, respectively. This method was used to fabricate a computer-generated hologram through Bragg-Berry (BB) phase that the phase of Bragg reflected light is modulated by controlling the azimuthal orientation of BPs. Furthermore, we theoretically and experimentally demonstrate that the BB hologram shows circular polarization selectivity for all angles of incidence, owing to the 3D helical structure of BPs.

There has been an increasing demand for fast and efficient random access pointing within emerging applications such as LiDAR, space based optical communications, displays, and autonomous vehicles. Particularly, Electro-Optical beam steering approaches have been considered to replace current mechanical beam steerers which are dominant technology in these applications. However, mechanical approaches have some issues such as mechanical complexity, pointing stability, high cost, bulky and heavy. Therefore, there is a need to replace mechanical steering devices with less costly nonmechanically scanned ones. Liquid Crystal-based devices are among the top candidates with promising performance. Last year, we have introduced a novel concept to design a tunable liquid crystal beam steering device using dual fringefield switching (FFS) cell to create an in-plane electric field with local control ability on the director of the liquid crystal [1]. The architecture allows to form a Pancharatnam Phase shape with continuous phase across an aperture without any resets. In this article, we will review optimization process of such a device to provide maximum output efficiency. Step by step optimization of design factors as well as material factors are explained, and an efficiency table is represented for comparison. Finally, sample experimental data is shown to match the modeling expectations for high efficiency.

We discuss the growth and shape stabilization of small objects made of smectic and nematic liquid crystals (NLCs) in aqueous surfactant solutions. When dispersed or put in contact with an aqueous solution of CTAB, smectic A liquid crystals spontaneously grow into fibers of very uniform diameter and good optical quality, which makes them appropriate for light guiding applications. However, it is difficult to control the growth of smectic A fibers and attempts to stabilize them by photo polymerization fail to produce good quality structures for optical application. We discuss a novel method for self-shaping of nematic liquid crystal droplets into various LC fibers. The method is based on the use of two surfactants: one is dissolved in the LC and the other in the aqueous phase. By changing the temperature, the surface of the droplet increases at a fixed volume of the LC, which triggers the transformation of a droplet into fibers. This is a novel mechanism of LC droplet shape transformation, where the surface of the LC interface is controlled by the temperature and concentration of two surfactants.

The effects of the anionic azo dye Sunset Yellow on the stabilization of lyotropic uniaxial and biaxial nematic phases and on the uniaxial to biaxial phase transitions were studied. The dye was added in different concentrations to the host ternary mixture of cationic surfactant dodecyltrimethylammonium bromide, 1-dodecanol, and water. Furthermore, an investigation examined the role of the dye in the lyotropic host mixture in comparison to some inorganic salts containing anions of the Hofmeister series.

We show photonic responses of selected two-dimensional photonic crystals that are based on a combination of geometrical design and spatial self-similarity. Structures based on multi-layer circles, squares, and triangles are studied, finding a range of local band gaps that can be varied with the self-similarity of the photonic crystal patterns. Selected photonic modes are shown that couple to different geometrical features of the photonic crystal. The role of boundary sharpness between the two dielectric components is emphasized.

Cholesteric liquid crystal (CLC) is a one-dimensional photonic crystal and is promising for various applications, including smart windows, optical components, and displays. Previous work has reported that polymer stabilized cholesteric liquid crystals (PSCLCs) have shown dynamic photonic properties with the application of direct current (DC) field, including bandwidth broadening, switchable scattering, red tuning and blue tuning. Recently, PSCLCs have been prepared upon exposure of a 363.8 nm Argon laser, and higher order diffraction peaks, such as the second and/or third order diffraction peaks, are observed. The higher order reflection bands are caused by the deformed helical structure of the polymer stabilizing network formed during the exposure of a single laser beam or under reflection grating conditions. The spectral position of the second-order reflection band, which is half the spectral position of the main CLC reflection band, is simply adjusted by chiral dopant concentrations in the CLC mixture. The selective main and higher order reflection notches can be red-tuned and broadened by the application of DC fields. A potential mechanism for higher order diffraction peaks in the PSCLCs will be discussed.