James N. Eakin

Liquid-crystal diffraction gratings using polarization holography alignment techniques

A method of patterning surfaces for liquid-crystal alignment using a polarization holography exposure on a linear photopolymerizable polymer alignment layer is demonstrated. Three configurations are demonstrated which include registered planar-periodic surface boundary conditions on both surfaces (true polarization gratings), planar-periodic and uniform planary surface boundary conditions, and planar-periodic and homeotropic boundary conditions. Two-dimensional polarization gratings are also demonstrated by orientating planar-periodic alignment layers orthogonally. Passive polarization gratings are also demonstrated using reactive mesogens to capture the periodic order indefinitely. The underlying structure of the configuration is discussed, including the nature of their switching transition (threshold or thresholdless), for all three configurations. A simple phenomenological model is presented to describe the Freedericksz transition for the registered planar-periodic boundary condition case.

Zero voltage Freedericksz transition in periodically aligned liquid crystals

Patterned alignment layers have been created through an approach using polarization holography and a photopolymerizable alignment layer. This technique enables continuously periodic boundary conditions on planar surfaces. Polarization gratings have been created using polarization interference from incident right-handed and left-handed circular polarization exposure conditions. A simple phenomenological model is derived to show that the Freedericksz threshold voltage vanishes when the cell gap and grating pitch are comparable.

Polymer scaffolding model for holographic polymer-dispersed liquid crystals

A polymer scaffolding model is proposed to describe the electro-optic performance parameters of holographic polymer-dispersed liquid crystals (H-PDLC). Using a simple phenomenological approach to model the interaction between the liquid crystal and polymer scaffolding, the observed increase in critical field and reduced dynamic response times are well described, and the molecular interaction energy is deduced to be ∼10−4 J/m2.

Holographic diffraction gratings using polymer-dispersed ferroelectric liquid crystals

By controlling the morphology of holographic polymer-dispersed ferroelectric liquid crystals (FLCs), highly aligned FLC domains are obtained for diffractive optical applications. Rapid, thresholdless switching is observed for various grating pitch sizes between approximately 3 and approximately 12 microm. A simple phenomenological model is presented encompassing a distribution of domain sizes and an effective field that stabilizes the FLC domains to reflect the observed thresholdless switching and optical behavior.

Polarization-selective switching in holographically formed polymer dispersed liquid crystals

We have developed an optical stack of holographically formed polymer dispersed liquid-crystal (H-PDLC) devices that is fully operational with nonpolarized light sources. The device consists of two H-PDLC transmission gratings separated by a passive polarization rotator that can output a diffracted s-polarized, p-polarized, or s- and p-polarized beam simultaneously.

24.3: Optical and Mechanical Properties of Stretched PDLC Films for Scattering Polarizers

By stretching (tensile strain)a polymer dispersed liquid crystal PDLC)film the liquid crystal droplets become elliptical and a polarization separation optical element is created. These films have significant potential as scattering polarizers in liquid crystal displays LCDs). We present a relationship between the polarization properties and the tensile strain properties of PDLC scattering polarizers. In addition, we present a modeling approach using a Monte-Carlo technique to predict the alignment of liquid crystals within the droplets and the details of their surface anchoring at the cavity wall. We also extend our investigation to reactive mesogen liquid crystal and higher order liquid crystal phases, such as ferroelectric and smectic A liquid crystal materials.

Polarization Holographic Patterned Alignment of Nematic Liquid Crystals

ABSTRACT We have successfully demonstrated a new way to pattern the alignment of liquid crystals using a linear photopolymerizable polymer (LPP) alignment layer with a polarization interference holographic exposure. This exposure method establishes a continuously periodic alignment of liquid crystals on the micrometer scale. In this contribution we show the various liquid crystal configurations that can be achieved through technique that have potential switchable diffractive optics applications.

Morphological Studies of Holographically formed Polymer Dispersed Ferroelectric Liquid Crystals

ABSTRACT In this contribution we describe a method to control and tailor the polarization sensitivity in holographically formed polymer dispersed liquid crystals (H-PDLCs) using a ferroelectric liquid crystal mixture with a UV curable diacrylate monomer. By controlling the FLC to monomer weight ratio we can radically manipulate the polarization sensitivity in these diffraction gratings. We show the polarization is related to the polymer morphology and hence the final alignment of the ferroelectric liquid crystal. We investigate the distinct morphologies (droplet and channel-like) into which the ferroelectric liquid crystal rich regions can be formed by imaging both the macroscopic and microscopic cross sections using optical polarizing microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM).

LP‐9: Late News Poster: Patterned Alignment Layers Using Holographic Exposure Technique

We present a novel method to create patterned alignment layers using holography with a photopolymerizable layer, and show the various types of alignments that are possible. The technique is very flexible and can create a rich variety of new configurations, not possible with conventional lithograph patterning techniques.

Laser Emission from Dye-Doped Liquid Crystal Gratings Formed by Polarization Holography

Laser emission from a nematic liquid crystal system whose grating structure is induced by a linear photopolymerizable alignment layer is reported. The grating structure is written on the alignment layer through polarization holography, inducing periodic boundary conditions on the laser dye-doped nematic liquid crystal. We report on the presence of laser emission at wavelengths predicted by coupled wave theory and the switchability of emission in these systems through the application of an electric field. Sensitivities to incident polarizations are also discussed.