Chiral columnar liquid crystals formed by chiral octahedral metallomesogenYoshida, Jun; Hara, Mitsuo; Watanabe, Go
doi: 10.1117/12.3029914pmid: N/A
The impact of molecular core chirality on helical columnar molecular assemblies has been investigated for enantiopure octahedral metallomesogens with propeller-shaped chirality. Although the inner stacking structures in helical columnar liquid crystals (Helical Col LCs) strongly affect the resultant functional properties such as ferroelectricity, there have been no definitive reported method to determine the inner structure. In this work, we used a combination of grazing-incidence (GI) X-ray diffraction spectroscopy and molecular dynamics (MD) simulations to reveal that the chiral octahedral metallomesogens stack with both the position and C3 axis rotating along the columnar axis. Therefore, the structure was classified as a hybrid of two proposed major helical stacking types; however, the detailed stacking structure of each type has not been sufficiently understood. Further structural analyses of the simulated structures highlight the interplay of the steric repulsion between the chiral cores, -stacking, and dipolar interactions in the helical formation. The accommodation of such weak interactions was confirmed for enantiopure samples by vibrational circular dichroism and UV-Vis spectroscopic studies, whereas racemic compounds were found to receive stronger intermolecular interactions to pack tightly.
Solid state LCPG (liquid crystal polarized grating) steerable cameraPhilipp, Tzvi
doi: 10.1117/12.3027627pmid: N/A
A solid-state steerable camera developed to generate high-resolution color images is presented. The camera can deliver greater than 16 MP resolution over a given field of view at a lower cost, in comparison to conventional camera systems. The camera incorporated a Liquid Crystal Polarized Grating (LCPG) structure, enabling imaging over an 87-degree field of view (FOV). The instantaneous field of view (iFOV) is approximately 10.4 degrees with a focal length of 17 mm, captured by a 2.1 MP sensor. The combined instantaneous fields of view generated by the eight independent steering directions cover the entire FOV. Images captured in ambient light via the LCPG imaging system suffer from chromatic dispersion due to the nature of the diffraction gratings. A narrow bandpass filter centered around 600 nm, is introduced to reduce the chromatic dispersion. A unique image processing neural network is used to correct residual spherochromatism generated by the LCPG device on a per iFOV basis. The entire system, encompassing the LCPG, voltage driver, optics, spectral filters, polarization filters, sensor, and neural network image processing program, has been used successfully in diverse operating conditions. The results show the viability of the steerable solid-state camera concept, highlighting its potential for high-resolution imaging with enhanced cost efficiency and reduced processing loads.
Vortex transitions on liquid crystal light valveDíaz-Zúñiga, M.; Aguilera-Rojas, P. J.
doi: 10.1117/12.3027434pmid: N/A
Optical vortex generation has attracted great interest in the scientific community due to its broad applicability in various technological developments. Several studies on optical vortex generation have been performed in liquid crystal media, specifically in transmission liquid crystal light valves; controlled and localized induction by light of optical vortex has been experimentally observed. An adequate amplitude equation, derived from first principles, describes this phenomenon. Theoretically, we find different localized vortex solutions depending on the bifurcation parameter. Experimentally, we analyze the transition point concerning voltage and intensity, proposing further investigation into these vortex-like solutions and their detailed characterization of structural transitions. The theoretical model of the liquid crystal light valve predicts several vortex structures that have not been studied experimentally. Based on a liquid crystal light valve experiment with applied light and voltage, we show the transition and appearance of different vortex structures. The study and detailed characterization of structures outside the limits predicted by the theory and possible corrections are proposed.
Novel plasma mirrors for petawatt (PW)-class lasers using ultrathin films of liquid crystalSchumacher, D. W.; Spingola, P. L.
doi: 10.1117/12.3028421pmid: N/A
Plasma mirrors are nonlinear optical components that, in their “off” state, have low reflectivity and high transmission. A high-intensity laser pulse will excite a plasma on the component surface triggering the “on”, high reflectivity state. Plasma mirrors are used to dynamically remove laser pre-pulse from ultrashort, ultrahigh intensity laser pulses, greatly increasing temporal pulse contrast. We have shown that free standing, ultrathin (<30 nm) films of the liquid crystal 8CB can serve as excellent, renewable plasma mirrors that can support pulses at powers up to 1 PW. The 8CB films have low vapor pressure and can be formed at high repetition rate inside a vacuum chamber at relatively low cost. More than conventional plasma mirrors using standard optical substrates, ultrathin films can facilitate versatile beam geometries for experiments via dynamic beam redirection. We have also introduced new computational models using both particle-in-cell simulations and empirical models. In this work, we describe both how free standing, ultrathin liquid crystal films can serve as excellent plasma mirrors and consider pathways to multi-PW operation, including use of liquid crystal mixtures.
Looking for planets with liquid crystal polymer opticsSerabyn, Eugene
doi: 10.1117/12.3027832pmid: N/A
Planar liquid-crystal-polymer (LCP) optical elements are increasingly being used to enable novel astronomical observational modes. These optical elements include diffractive waveplates for spectropolarimetry, optical vortex phase masks for high-contrast stellar coronagraphy, pupil-plane phase masks for both beam shaping and nulling interferometry, and Zernicke phase masks for wavefront sensing. Several of these devices have already been used on ground-based telescopes, and further development may ultimately enable these techniques to be used to detect and measure spectra of Earth-like exoplanets around nearby stars.
Single-emitter nanocrystal fluorescence in liquid crystal hosts: nonclassical light sources with definite polarizationLukishova, Svetlana G.
doi: 10.1117/12.3027883pmid: N/A
Overview is presented on using liquid crystals in single-photon sources (SPSs) exhibiting antibunching (separation of all photons in time) with definite linear or circular polarizations. SPSs are key components for secure, long-distance quantum communication systems with quantum repeaters. If we can produce a photon with definite polarization, the efficiency of the quantum cryptography system is doubled. Both nematic and cholesteric liquid crystal (CLC) hosts were used to create definite linear or circular polarization of antibunched photons emitted by different types of single emitters (dye molecules, colloidal semiconductor nanocrystal quantum dots (NQDs) with different fluorescence wavelengths, nitrogen-vacancy (NV) color-center nanodiamonds). Definite polarization from nanocrystals doped with trivalent rare-earth ions in liquid crystal hosts at low light level is also reported. Both monomeric and glassy oligomeric liquid crystal hosts have been used. Raman scattering in monomeric liquid crystals can prevent photon antibunching at some fluorescence wavelengths. A circular polarized microcavity resonance in NQD fluorescence in a 1-D photonic bandgap CLC microcavity and spontaneous emission enhancement as well as some pitfalls on purity of single-photon emission with using photoalignment materials are discussed (photoalignment materials’ fluorescence imaging may show single-emitter fluorescence behavior with emission of antibunched light).
Research on liquid crystal-based smart windows for application of building-integrated solar power systemKi, Hyun Chul; Chung, Da Yeon; Kwon, Tae-Hyuk; Im, Sung Jun; Park, Hong Gyu; Kim, Jae Hwan
doi: 10.1117/12.3027398pmid: N/A
Smart windows are active windows that can adjust transmittance and can perform functions such as energy saving, indoor illumination control in conjunction with smart lighting or daylighting, user privacy protection, and active space separation. Smart window technology has high potential to expand not only to buildings but also to next-generation mobility fields such as electric vehicles and air taxis. Types of smart windows include electrochromic type(EC), polarized particle type(PP), and liquid crystal type(LC). In the case of liquid crystal systems, polymer dispersed liquid crystal systems (PDLC) are being developed the most. However, the PDLC has the advantage of fast response speed, but has the disadvantage of high driving voltage and difficulty in realizing color. In this study, we developed a liquid crystal-based smart window capable of low-power operation and color implementation that can be combined with building-integrated solar power to save energy in buildings. In order to realize color, dyes were developed in a way that did not affect the liquid crystal. And in order to apply it to building windows, we developed a liquid crystal smart window that can operate without a polarizer for arrangement of liquid crystals, which is different from the existing liquid crystal method by considering transmittance. As a result of measuring the color, operating voltage, and current of the liquid crystal smart window, the CIE-LAB index difference for color was 20.86 (L: 41.33 34.23, a: - 10.43 -3.25, b: -9.88 -3.3), The voltage was 5V and the current was 4.14X10-7[A]. In addition, the driving voltage and current result was 2.07uW, confirming that low-power driving was possible.
Reliable method to characterise parameters and surface effects in wedge and thin liquid crystal cellsStedman, Ben; Beddoes, Ben; Bankova, Denitsa; Podoliak, Nina; D'Alessandro, Giampaolo; Buchnev, Oleksandr; Kaczmarek, Malgosia
doi: 10.1117/12.3029036pmid: N/A
Augmented and virtual reality displays require the use of thin liquid crystal cells, with thickness of the order of 1-2 µm. Here, we demonstrate a method, based on cross-polarised intensity measurements coupled to a Frank-Oseen model of the liquid crystal alignment, to characterise such thin cells and the interactions between the liquid crystal and the cell substrates. We first use wedge shaped cells to calibrate the measurement process and show that the cross-polarised intensity data can be used to reliably characterise cells with a non-uniform thickness profile. Previously, we have shown that we can characterise optically thin cells (cells with a phase lag of less than 2). In this report we apply the method to characterise the optical properties of cells with a non-uniform thickness profile and geometrically thin cells. We show that reducing the thickness of the cell increases the pretilt.
Smectic layer influence induced by surface anchoring on its dynamic optical response behaviorMochizuki, Akihiro
doi: 10.1117/12.3027866pmid: N/A
Influence of surface pre-tilt setting on dynamic initial driving torque of an SSD (Smectic Single Domain) liquid crystal drive mode has been investigated. Unlike typical nematic liquid crystal drive mode, a smectic liquid crystal drive mode has some significant influence by its smectic layer switching behavior. To clarify the layer switching influence, an initial driving torque was investigated how the initial torque was formed, how the torque interacted to the dynamic layer distortion behavior, and so on. Empirical approaches included both dielectric relaxation behavior and dynamic retardation switching behavior. These measurements suggested that the initial surface pre-tilt setting was one of the primary influential factors to govern dynamic optical response profile of an SSD-LC panel.
Nonlinear wave propagation in a bistable optical chain with controlled non-reciprocal couplingAguilera-Rojas, Pedro J.; Díaz-Zúñiga, Manuel
doi: 10.1117/12.3027844pmid: N/A
Bistable coupled systems can exhibit nonlinear waves. Domino waves represent a straightforward example of nonlinear waves in everyday life. Domino waves are observed in extended bistable chains where a domino has two stable equilibria: vertical and horizontal. These elements are coupled reciprocally. Namely, if one exchanges the role of emitter and receiver, the observed propagation is the same. Nonetheless, there is no knowledge of the impact of non-reciprocal coupling on the propagation of nonlinear waves. Based on an experiment using a liquid crystal light valve (LCLV) with optical feedback, non-reciprocal nonlinear wave propagation can be studied in a one-dimensional chain discrete model. A spatial light modulator and an optical feedback loop let us control the initial conditions and non-reciprocal coupling, respectively. The nonlinear waves' spatiotemporal evolution and velocities are also characterized. A discrete model of the bistable system is derived using a tight binding-like approach for the LCLV with non-reciprocal optical feedback. Numerical simulations of the non-reciprocal coupled bistable system reasonably agree with experimental observations.