Mark A. Handschy

Ferroelectric Liquid Crystal Electro-Optics Using the Surface Stabilized Structure

Abstract The strong linear coupling of the director ň to electric field E in ferroelectric liquid crystals can be utilized to perform high-speed electro-optic switching suitable for device applications. In this article we summarize the current understanding of the high-speed, bistable, threshold-sensitive electro-optic effects obtained in planar structures using surface interactions to suppress the spontaneous director helix characteristic of the bulk ferroelectric liquid crystal.

High-speed binary optically addressed spatial light modulator

We describe the structure and operating characteristics of a high‐speed optically addressed spatial light modulator (OASLM) with a hydrogenated amorphous silicon (a‐Si:H) photosensor and a ferroelectric liquid‐crystal modulator. The photosensor is a p‐i‐n photodiode, which switches the liquid crystal into one of two stable states. Under a write‐light intensity of 6 mW/cm2, the OASLM exhibits a response time of 155 μs, a contrast ratio of 20:1, and a resolution of 40 lp/mm. The writing sensitivity per pixel is 0.1 pJ.

Ferroelectric-liquid-crystal/silicon-integrated-circuit spatial light modulator

We present the design and characterization of a spatial light modulator (SLM) comprising a ferroelectric-liquid-crystal light-modulating layer on top of a silicon integrated circuit. Our SLM consists of two electrically addressed arrays on the same integrated-circuit die. The first, a 1 x 128 linear array with a 20-microm center-to-center element spacing, used shift register addressing, while the second, a 64 x 64 square array with 60-microm pitch, used static random access memory addressing. The resulting SLM could be addressed at frame rates of up to 4.5 kHz and gave singleelement intensity contrast ratios of 12:1.

Electrooptic response during switching of a ferroelectric liquid crystal cell with uniform director orientation

We present calculations of the light intensity transmitted through a uniform ferroelectric liquid crystal light valve during electrooptic switching. We discuss the calculated delay time and rise time of the optical response, and show how they depend on spontaneous polarization, dielectric anisotropy, applied electric field, and initial director orientation. Our calculations also yield the ferroelectric polarization-reversal current.

Stroboscopic microscopy of fast electro‐optic switching in ferroelectric smectic C liquid crystals

We have characterized the process that yields high‐speed, bistable, electro‐optic switching in the surface‐stabilized ferroelectric liquid crystal geometry, at intermediate electric fields. Switching proceeds by a continuous reversal of ferroelectric polarization in regions away from the surfaces of the sample, followed by the nucleation and growth of domains of reversed polarization in the remaining surface layers. A model involving bulk distortion+electrostatic+surface free energy successfully accounts for the variation of the switching process with changes in applied electric field.

Optical Computing And Image Processing With Ferroelectric Liquid Crystals

High-contrast, submicrosecond switching ferroelectric liquid crystal spatial light modulators have many applications to optical computing and image processing. In this paper we describe the use of these low-voltage, low-power, and bistable devices to perform a variety of functions including polarization- and intensity-based logic gates, input/output displays, optical crossbars, and spatial filtering masks.

Director reorientation dynamics in chevron ferroelectric liquid crystal cells

Abstract We present sample numerical solutions of the equation of motion that governs the dynamics of molecular orientation in ferroelectric liquid crystal cells with chevron layer structure. We show that the chevron structure significantly influences the director field, the chevron interface providing surface stabilization on a plane interior to the FLC layer. Assuming non-polar nematic-like elasticity in the vicinity of the chevron interface, we have modelled the effects of applied field on cells with purely non-polar cell boundary interactions that have uniform director orientation at zero field, and on cells in which the cell walls are strongly polar and the zero-field states are splayed. The simulations with strongly polar surfaces give bistable operation with the two states having fixed orientations at the FLC-solid surfaces, different orientation of P at the chevron interface, and P splayed in either the upper or lower portion of the cell. A monostable state can arise when the chevron interface is ...

Director orientation in chevron surface-stabilized ferroelectric liquid crystal cells. Verification of orientational binding at the chevron interface using visible polarized light transmission spectroscopy

Abstract We present results of theoretical modelling and experimental study of director distributions and the associated optical properties of chevron surface stabilized ferroelectric liquid crystal (SSFLC) cells. Chevron cells are modelled as being two stacked FLC slabs, described by distinct orientation distributions of the director [ncirc]-polarization P([ncirc] – P) couple. In each slab the [ncirc] – P distribution is governed by bulk Frank elastic and electric field-induced torques and by surface torques at the FLC-solid interface and at the chevron interface, where the two distributions are coupled. The optical properties of such structures are calculated numerically and the results tested using polarized light microscope-based spectrophotometric measurements of the wavelength dependent transmission of chevron SSFLC cells with varying sample orientation and applied field. Measured transmission spectra agree quantitatively with the model and provide evidence for the constraint of the ň – P field at t...

Evaluation of a proposal for reliable low-cost grid power with 100% wind, water, and solar

A number of analyses, meta-analyses, and assessments, including those performed by the Intergovernmental Panel on Climate Change, the National Oceanic and Atmospheric Administration, the National Renewable Energy Laboratory, and the International Energy Agency, have concluded that deployment of a diverse portfolio of clean energy technologies makes a transition to a low-carbon-emission energy system both more feasible and less costly than other pathways. In contrast, Jacobson et al. [Jacobson MZ, Delucchi MA, Cameron MA, Frew BA (2015) Proc Natl Acad Sci USA 112(49):15060–15065] argue that it is feasible to provide “low-cost solutions to the grid reliability problem with 100% penetration of WWS [wind, water and solar power] across all energy sectors in the continental United States between 2050 and 2055”, with only electricity and hydrogen as energy carriers. In this paper, we evaluate that study and find significant shortcomings in the analysis. In particular, we point out that this work used invalid modeling tools, contained modeling errors, and made implausible and inadequately supported assumptions. Policy makers should treat with caution any visions of a rapid, reliable, and low-cost transition to entire energy systems that relies almost exclusively on wind, solar, and hydroelectric power. Significance Previous analyses have found that the most feasible route to a low-carbon energy future is one that adopts a diverse portfolio of technologies. In contrast, Jacobson et al. (2015) consider whether the future primary energy sources for the United States could be narrowed to almost exclusively wind, solar, and hydroelectric power and suggest that this can be done at “low-cost” in a way that supplies all power with a probability of loss of load “that exceeds electric-utility-industry standards for reliability”. We find that their analysis involves errors, inappropriate methods, and implausible assumptions. Their study does not provide credible evidence for rejecting the conclusions of previous analyses that point to the benefits of considering a broad portfolio of energy system options. A policy prescription that overpromises on the benefits of relying on a narrower portfolio of technologies options could be counterproductive, seriously impeding the move to a cost effective decarbonized energy system.

Hydrogenated amorphous-silicon photosensor for optically addressed high-speed spatial light modulator

A high-speed, optically addressed spatial light modulator (OASLM) which incorporates a hydrogenated amorphous silicon (a-Si:H) photosensor and a ferroelectric liquid-crystal (FLC) modulator is discussed. The device operates with an applied square-wave voltage such that read and write operations occur under reverse bias, while the erase operation occurs under forward bias. The OASLM exhibits a response time of 155 mu s and a spatial resolution of >33 1p/mm. The capacitance and resistance of both the a-Si:H and FLC have been measured and are shown to influence the response of the device strongly. >