Diffraction and fringing field effects in small pixel liquid crystal devices with homeotropic alignment

Vanbrabant, Pieter; Beeckman, Jeroen; Neyts, Kristiaan; Willman, Eero; Fernández, FA

doi:10.1063/1.3499279

Cited by 12 publications

(6 citation statements)

References 25 publications

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“…62 As a result, the 2π phase transition is not only continuous because of the finite extent of the elastic deformation, but the flyback region is also elongated due to fringing fields. [63][64][65] The flyback region is the distance over which the 2π phase jump is smeared out. It has been shown that this effect is detrimental for the steering efficiency η at large angles θ .…”

Section: Laser Beam Steeringmentioning

confidence: 99%

Liquid-crystal photonic applications

2011

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Abstract. Liquid crystals are nowadays widely used in all types of display applications. However their unique electro-optic properties also make them a suitable material for nondisplay applications. We will focus on the use of liquid crystals in different photonic components: optical filters and switches, beam-steering devices, spatial light modulators, integrated devices based on optical waveguiding, lasers, and optical nonlinear components. Both the basic operating principles as well as the recent state-of-the art are discussed. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).[ DOI: 10.1117/1.3565046] Subject terms: liquid crystals; photonic applications; review; liquid-crystal lasers; spatial light modulators; tunable lenses; nematicons; optical nonlinearity.Paper 100913SSR received Nov. 5, 2010; revised manuscript received Jan. 11, 2011; accepted for publication Jan. 13, 2011; published online Jun. 14, 2011. IntroductionLiquid crystals (LCs) are organic materials that are liquid but that show a certain degree of ordering (positional and/or orientational). With this definition, many materials can be classified as liquid crystals, but the majority of liquid crystals that are used in photonic applications are of the thermotropic type. Thermotropic means that the liquid-crystal phase exists within a certain temperature interval (in contrast to lyotropic materials for which the material is liquid-crystal within a certain concentration range). Various types of thermotropic liquid-crystal materials exist, and many different mesophases have been discovered in the last decades: nematic, smectic A, smectic C, columnar, blue phases, and many many more. The diversity of liquid-crystal materials is huge, but this diversity is even overshadowed by the number of applications in which liquid crystals are used nowadays. The majority of applications are related to informationdisplay applications. Liquid crystals have conquered the major market share in different display application areas: television screens, laptop screens, screens in mobile phones, etc. Only in projection displays does a tough competitor exist, namely microelectromechanical systems or licenced by Texas Instruments: Digital light processing. Organic light emitting diodes (OLEDs) are the obvious next generation technology that could overtake the LC domination, but today OLED displays have not penetrated the market and only the future will tell if they will. In this review article, we will focus on nondisplay applications, but because we cannot go too broad, we restrict ourselves to photonic applications in which the light is actively manipulated by the LC. In this review article, a certain external influence (surface anchoring, electric fields, optical fields) is used to (re)orient the LC in a certain way. In turn, the LC then changes the light that is propagating through it. Of course, as in every review article, it is impossible to list all the fascinating new scientific results or breakthroughs. Therefore, the authors apologize for not i...

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Section: Laser Beam Steeringmentioning

confidence: 99%

Liquid-crystal photonic applications

2011

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“…Interesting to note is that in the reference device domain walls are apparent, which collapse into disclination lines at higher voltages (∼7.8 V, see Visualization 1). The reason for their appearance is the presence of strong in-plane fringe fields which tilt the LC in a direction opposite to the one imposed by the pretilt [23], as shown by the simulation result of Fig. 4(a), which is a visualization of the director profile along the slice indicated in Fig.…”

Section: Measurements and Discussionmentioning

confidence: 97%

Ferroelectric thin films with liquid crystal for gradient index applications

Willekens¹,

George²,

Neyts³

et al. 2016

Opt. Express

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We report on the first ever combination of a thin film of lead zirconate titanate (PZT) with a liquid crystal (LC) layer. Many liquid crystal applications use a transparent conductive oxide to switch the liquid crystal. Our proposed processing does not, instead relying on the extremely high dielectric constant of the ferroelectric layer to extend the electric field from widely spaced electrodes over the liquid crystal. It eliminates almost entirely the fringe field problems that arise in nearly all the liquid crystal devices that use multiple addressing electrodes. We show, both via rigorous simulations as well as experiments, that the addition of a PZT layer over the addressing electrodes leads to a markedly improved LC switching performance at distances of up to 30 µm from the addressing electrodes with the current PZT-layer thickness of 0.84 µm. This improvement in switching is used to tune the focal length of the microlens with electrodes spaced at 30 µm.

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“…FFE is especially pronounced in small-pitch LCoS devices [69], which is highly desirable in augmented reality applications. Because of the reduced pixel pitch and cell gap (p/d) ratio, the unwanted horizontal electric field is strengthened [70]. This can be seen from Figure 6b: when the resolution density is doubled (p changes from 16 µm to 8 µm), the absolute FFE width w is relatively stable, while the ratio of the FFE-affected region increases dramatically.…”

Section: Fringing Field Effect and Novel Solutionmentioning

confidence: 98%

“…To optimize the optical performance of LCoS systematically, several research groups have devoted efforts in device modeling [65][66][67]. However, until recently, the fringing field effect (FFE) still remains the major issue to be tackled with [68][69][70][71][72][73]. In order to display greyscale images, different pixels could have different voltages.…”

Section: Fringing Field Effect and Novel Solutionmentioning

confidence: 99%

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Liquid-Crystal-on-Silicon for Augmented Reality Displays

Huang

Liao²,

Chen

et al. 2018

Applied Sciences

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In this paper, we review liquid-crystal-on-silicon (LCoS) technology and focus on its new application in emerging augmented reality (AR) displays. In the first part, the LCoS working principles of three commonly adopted LC modes—vertical alignment and twist nematic for amplitude modulation, and homogeneous alignment for phase modulation—are introduced and their pros and cons evaluated. In the second part, the fringing field effect is analyzed, and a novel pretilt angle patterning method for suppressing the effect is presented. Moreover, we illustrate how to integrate the LCoS panel in an AR display system. Both currently available intensity modulators and under-developing holographic displays are covered, with special emphases on achieving high image quality, such as a fast response time and high-resolution. The rapidly increasing application of LCoS in AR head-mounted displays and head-up displays is foreseeable.

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Diffraction and fringing field effects in small pixel liquid crystal devices with homeotropic alignment

Cited by 12 publications

References 25 publications

Liquid-crystal photonic applications

Liquid-crystal photonic applications

Ferroelectric thin films with liquid crystal for gradient index applications

Liquid-Crystal-on-Silicon for Augmented Reality Displays

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