Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Spatial Frequency Responses of Anisotropic Refractive Index Gratings Formed in Holographic Polymer Dispersed Liquid Crystals.

ABSTRACT: We report on an experimental investigation of spatial frequency responses of anisotropic transmission refractive index gratings formed in holographic polymer dispersed liquid crystals (HPDLCs). We studied two different types of HPDLC materials employing two different monomer systems: one with acrylate monomer capable of radical mediated chain-growth polymerizations and the other with thiol-ene monomer capable of step-growth polymerizations. It was found that the photopolymerization kinetics of the two HPDLC materials could be well explained by the autocatalytic model. We also measured grating-spacing dependences of anisotropic refractive index gratings at a recording wavelength of 532 nm. It was found that the HPDLC material with the thiol-ene monomer gave higher spatial frequency responses than that with the acrylate monomer. Statistical thermodynamic simulation suggested that such a spatial frequency dependence was attributed primarily to a difference in the size of formed liquid crystal droplets due to different photopolymerization mechanisms.

SUBMITTER: Fukuda Y

PROVIDER: S-EPMC5456659 | biostudies-other | 2016 Mar

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

Low-threshold distributed feedback laser based on holographic polymer dispersed liquid crystals through the oriented organic semiconductor films.

Project description:A specific optimized configuration for low threshold organic semiconductor laser based on a holographic polymer dispersed liquid crystal (HPDLC) transmission grating was demonstrated. Here the organic semiconductor films and phase separated liquid crystal (LC) molecules were oriented along the direction of the HPDLC grating grooves. The influence of the organic semiconductor chain orientation and the excitation polarization on the optical properties of the materials has been investigated. Especially, when polymer chain orientation, LC molecules and pump light polarization are consistent with the direction of the grating grooves, the performance of the outgoing laser is greatly improved. Up to 9.78% conversion efficiency with a threshold lower to 0.12 μJ/pulse can be obtained, indicating their potential for high-performance organic optoelectronics.

| S-EPMC11294608 | biostudies-literature

Dirac directional emission in anisotropic zero refractive index photonic crystals.

Project description:A certain class of photonic crystals with conical dispersion is known to behave as isotropic zero-refractive-index medium. However, the discrete building blocks in such photonic crystals are limited to construct multidirectional devices, even for high-symmetric photonic crystals. Here, we show multidirectional emission from low-symmetric photonic crystals with semi-Dirac dispersion at the zone center. We demonstrate that such low-symmetric photonic crystal can be considered as an effective anisotropic zero-refractive-index medium, as long as there is only one propagation mode near Dirac frequency. Four kinds of Dirac multidirectional emitters are achieved with the channel numbers of five, seven, eleven, and thirteen, respectively. Spatial power combination for such kind of Dirac directional emitter is also verified even when multiple sources are randomly placed in the anisotropic zero-refractive-index photonic crystal.

| S-EPMC4536485 | biostudies-other

Optical Properties of Electrically Tunable Two-Dimensional Photonic Lattice Structures Formed in a Holographic Polymer-Dispersed Liquid Crystal Film: Analysis and Experiment.

Project description:We report on theoretical and experimental investigations of optical wave propagations in two-dimensional photonic lattice structures formed in a holographic polymer-dispersed liquid crystal (HPDLC) film. In the theoretical analysis we employed the 2×2 matrix formulation and the statistical thermodynamics model to analyze the formation of anisotropic photonic lattice structures by holographic polymerization. The influence of multiple reflections inside an HPDLC film on the formed refractive index distribution was taken into account in the analysis. In the experiment we fabricated two-dimensional photonic lattice structures in an HPDLC film under three-beam interference holographic polymerization and performed optical measurements of spectral transmittances and wavelength dispersion. We also demonstrated the electrical control capability of the fabricated photonic lattice structure and its dependence on incident wave polarization. These measured results were compared with the calculated ones by means of photonic band and beam propagation calculations.

| S-EPMC5453218 | biostudies-other

Polymer Dispersed Cholesteric Liquid Crystals With a Toroidal Director Configuration under an Electric Field.

Project description:The electro-optical properties of polymer dispersed liquid crystal (PDLC) films are highly dependent on the features of the contained liquid crystal (LC) droplets. Cholesteric LC droplets with homeotropic boundaries can form several topologically different orientational structures, including ones with single and more point defects, layer-like, and axisymmetric twisted toroidal structures. These structures are very sensitive to an applied electric field. In this work, we have demonstrated experimentally and by computer simulations that twisted toroidal droplets reveal strong structural response to the electric field. In turn, this leads to vivid changes in the optical texture in crossed polarizers. The response of droplets of different sizes were found to be equivalent in terms of dimensionless parameters. In addition, the explanation of this phenomenon showed a comparison of theoretical and experimental structural response curves aids to determine the shape of the droplet. Finally, we demonstrated that the addition of a dichroic dye allows such films to be used as optical filters with adjustable color even without polarizers.

| S-EPMC7956821 | biostudies-literature

Polymer-dispersed liquid crystal elastomers.

Project description:The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations.

| S-EPMC5059788 | biostudies-literature

Diffractive Optical Analysis for Refractive Index Sensing using Transparent Phase Gratings.

Project description:We report the implementation of a micro-patterned, glass-based photonic sensing element that is capable of label-free biosensing. The diffractive optical analyzer is based on the differential response of diffracted orders to bulk as well as surface refractive index changes. The differential read-out suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6 × 10(-7) was achieved with this technique with scope for further improvement.

| S-EPMC4649337 | biostudies-literature

Modal energy transfer by thermally induced refractive index gratings in Yb-doped fibers.

Project description:Thermally induced refractive index gratings in Yb-doped fibers lead to transverse mode instability (TMI) above an average power threshold, which represents a severe problem for many applications. To obtain a deeper understanding of TMI, the evolution of the strength of the thermally induced refractive index grating with the average output power in a fiber amplifier is experimentally investigated for the first time. This investigation is performed by introducing a phase shift between the refractive index grating and modal interference pattern, which is obtained by applying a pump power variation to the fiber amplifier. It is demonstrated that the refractive index grating is sufficiently strong to enable modal energy coupling at powers that are significantly below the TMI threshold if the induced phase shift is sufficiently large. The experiments indicate that at higher powers, the refractive index grating becomes more sensitive to such phase shifts, which will ultimately trigger TMI. Furthermore, the experimental results demonstrate beam cleaning above the TMI threshold via the introduction of a positive phase shift. This finding paves the way for the development of a new class of mitigation strategies for TMI that are based on controlling the phase shift between the thermally induced refractive index grating and modal interference pattern.

| S-EPMC6123421 | biostudies-literature

Refractive index matched, nearly hard polymer colloids.

Project description:Refractive index matched particles serve as essential model systems for colloid scientists, providing nearly hard spheres to explore structure and dynamics. The poly(methyl methacrylate) latexes typically used are often refractive index matched by dispersing them in binary solvent mixtures, but this can lead to undesirable changes, such as particle charging or swelling. To avoid these shortcomings, we have synthesized refractive index matched colloids using polymerization-induced self-assembly (PISA) rather than as polymer latexes. The crucial difference is that these diblock copolymer nanoparticles consist of a single core-forming polymer in a single non-ionizable solvent. The diblock copolymer chosen was poly(stearyl methacrylate)-poly(2,2,2-trifluoroethyl methacrylate) (PSMA-PTFEMA), which self-assembles to form PTFEMA core spheres in n-alkanes. By monitoring scattered light intensity, n-tetradecane was found to be the optimal solvent for matching the refractive index of such nanoparticles. As expected for PISA syntheses, the diameter of the colloids can be controlled by varying the PTFEMA degree of polymerization. Concentrated dispersions were prepared, and the diffusion of the PSMA-PTFEMA nanoparticles as a function of volume fraction was measured. These diblock copolymer nanoparticles are a promising new system of transparent spheres for future colloidal studies.

| S-EPMC6598067 | biostudies-literature

Anisotropic, porous hydrogels templated by lyotropic chromonic liquid crystals.

Project description:Approaches to control the microstructure of hydrogels enable the control of cell-material interactions and the design of stimuli-responsive materials. We report a versatile approach for the synthesis of anisotropic polyacrylamide hydrogels using lyotropic chromonic liquid crystal (LCLC) templating. The orientational order of LCLCs in a mold can be patterned by controlling surface anchoring conditions, which in turn patterns the polymer network. The resulting hydrogels have tunable pore size and mechanical anisotropy. For example, the elastic moduli measured parallel and perpendicular to the LCLC order are 124.9 ± 6.4 kPa and 17.4 ± 1.1 kPa for a single composition. The resulting anisotropic hydrogels also have 30% larger swelling normal to the LCLC orientation than along the LCLC orientation. By patterning the LCLC order, this anisotropic swelling can be used to create 3D hydrogel structures. These anisotropic gels can also be functionalized with extracellular matrix (ECM) proteins and used as compliant substrata for cell culture. As an illustrative example, we show that the patterned hydrogel microstructure can be used to direct the orientation of cultured human corneal fibroblasts. This strategy to make anisotropic hydrogels has potential for enabling patternable tissue scaffolds, soft robotics, or microfluidic devices.

| S-EPMC9017599 | biostudies-literature

Tunable High Refractive Index Polymer Hybrid and Polymer-Inorganic Nanocomposite Coatings.

Project description:Atomized spray plasma deposition (ASPD) provides a single-step, low-temperature, and dry approach for the preparation of high refractive index hybrid polymer or polymer-inorganic nanocomposite coatings. Refractive indices as high as 1.936 at 635 nm wavelength have been obtained for ASPD 4-bromostyrene/toluene-TiO2 nanocomposite layers containing low titania loadings. Thin films with any desired refractive index up to 1.936 can be easily deposited onto a variety of substrates by varying the precursor mixture composition. ASPD overcomes disadvantages commonly associated with alternative fabrication methods for depositing high refractive index coatings (elevated temperatures, wet processes, UV curing steps, and much greater inorganic loadings).

| S-EPMC8397253 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data