The role of surface charge field in two-beam coupling in liquid crystal cells with photoconducting polymer layers

Kaczmarek, Malgosia; Dyadyusha, A.; Slussarenko, S.; Khoo, I. C.

doi:10.1063/1.1778818

Cited by 91 publications

(50 citation statements)

References 27 publications

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“…When the driving frequency of the write light is higher than a few tens of hertz, the modulation of the read light in accordance with the write light is no longer visible. This is most likely because the write time is insufficient to produce the charge distribution needed for the realignment of the photosensor-LC interface layer 29 as a result of the high defect density in the NPs. 17 Further research is needed to increase the refresh rate of such a system.…”

Section: High-resolution Oaslm Based On Zno Nanoparticles Pk Shresthamentioning

confidence: 97%

A high-resolution optically addressed spatial light modulator based on ZnO nanoparticles

2015

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An optically addressed spatial light modulator (OASLM) can modulate the wavefront of a read light by displaying a phase pattern or a hologram configured by the intensity distribution of a write light. Using ZnO nanoparticles (NPs) as a novel photoconductor, a high-resolution OASLM was fabricated. A ZnO NP suspension was spin-coated on an indium tin oxide (ITO)-coated glass substrate and annealed to form a photosensitive layer. The device was characterized electrically and optically. The device was operated at low driving voltages in the transmission mode. Updatable recording of a diffraction grating up to 825 lp mm 21 with a diffraction efficiency (DE) of 0.05% and binary holograms with pixel sizes from 2 mm down to 0.72 mm were demonstrated using a 405 nm wavelength write laser and a 635 nm wavelength read laser.

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Section: High-resolution Oaslm Based On Zno Nanoparticles Pk Shresthamentioning

confidence: 97%

A high-resolution optically addressed spatial light modulator based on ZnO nanoparticles

2015

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“…Kaczmarek et al 17 where the authors studied C 60 doped polymers as photorefractive surfaces in LC cell. However, our cells differ by the thickness of the photorefractive layer.…”

Section: Devices and Materialsmentioning

confidence: 99%

PROJECTION OF HOLOGRAMS FROM PHOTOREFRACTIVE OASLMs

Trushkevych

Collings

Crossland

et al. 2007

J. Nonlinear Optic. Phys. Mat.

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Liquid crystals doped with fullerenes and carbon nanotubes (CNTs) act as good optical nonlinear materials. We have used these materials to build optically addressed spatial light modulators (OASLMs). The devices comprise of single layer of doped liquid crystal acting as an active layer. Undoped LC devices with surfaces coated with fullerenes are also studied.Such OASLMs allow recording of phase holograms, and we record by imaging pre-calculated pre-recorded holograms. Writing is performed at normal incidence and reading at 45 o oblique incidence. Both, transmission and reflection modes of operation are used. Experimental results as well as comparison with commercially available OASLMs are presented.Keywords: optically addressed spatial light modulator (OASLM), holography, fullerene, carbon nanotube, liquid crystal, optical nonlinear materials, photorefractivity. IntroductionSpatial light modulators (SLMs) are devices that can record two-dimensional images and erase the previously recorded image. They are increasingly used in many applications including video and display applications 1 and real-time holography 2 . Electrically addressed SLMs are * or213@cam.ac.uk; phone +44 1223 748347; fax +44 1223 748348; http://www-g.eng.cam.ac.uk/photonics 2 expensive, and due to limitations on the driving circuitry the number of addressable pixels is limited. To simplify the system, one can address SLMs directly by light.Optically addressed spatial light modulators (OASLMs) are already commercially available (Hamamatsu † ). These devices are based on adjacent amorphous silicon and Liquid Crystal (LC) layers. They are relatively simple, but still hard to manufacture and can be used only in reflection at visible wavelengths. Dye-doped LC systems are highly promising materials for novel OASLMs based on photorefractive orientational effects. 3-9 Such devices are intrinsically photorefractive without the need of special layers or circuitry, therefore there are no strict technological limitations on the device area. They can be used in transmission as well as reflection, and measurements show that the resolution of 1-layer dye-doped-LC device can be better than that of the 2-layer amorphous silicon OASLM. 10 Target characteristics for photorefractive OASLMs are 2 phase modulation and fast switching (e.g. at least 20 ms for video applications). The devices are also expected to have low power consumption, low cost, high resolution (~ 10m) and good lifetime.Nematic liquid crystals doped with fullerenes 6,11,12 and carbon nanotubes 13,14 are recognised for their extraordinary large optical nonlinearities with nonlinear refractive index coefficient n 2 up to 20 cm 2 /W 11,12 . It is believed that the nonlinearities are due to the reorientation of the nematic director which occurs due to light-induced space-charge field formation aided by the dopant 6 .In this work we report performance of transmissive and reflective photorefractive OASLMs based on a single layer of fullerene or carbon nanotube doped nematic liquid crystals. Undoped L...

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“…However, as our model shows, for modulated electric fields integrated in one structure with two polymer surfaces, the effect is equally important. Such consideration is particularly relevant when considering active aligning layers such as photosensitive polymers [14] and liquid crystal metamaterials [20].…”

Section: Introductionmentioning

confidence: 99%

“…As a test structure we consider a typical photorefractive cell that includes a photoconductive alignment layer and a nematic liquid crystal [14], illustrated schematically in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

“…Two standard examples of such devices in widespread use are spatial light modulators [4][5][6][7][8][9][10][11] and photorefractive cells [12][13][14][15][16]. The common mode of operation of these and other liquid crystal devices is that the voltage applied to the liquid crystal has a uniform component, required to move the liquid crystal past the Fredericks transition, and a generally weaker spatially modulated component that creates a nonuniform director alignment field in the liquid crystal.…”

Section: Introductionmentioning

confidence: 99%

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Optimal liquid crystal modulation controlled by surface alignment and anchoring strength

et al. 2012

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Spatial modulation of liquid crystals can be controlled and adjusted by light polarization, the degree of pretilt on the substrates, anchoring strength, and the experimental geometry. In particular, strong anchoring can affect the liquid crystal orientation in opposite ways, depending on the polarization of the incident light. Here we present a theoretical model that describes the liquid crystal modulation and how it can be controlled and optimized. The model is valid for electric fields with a uniform component that is large with respect to the spatial modulation, a situation typical of spatial light modulators and photorefractive cells.

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The role of surface charge field in two-beam coupling in liquid crystal cells with photoconducting polymer layers

Cited by 91 publications

References 27 publications

A high-resolution optically addressed spatial light modulator based on ZnO nanoparticles

A high-resolution optically addressed spatial light modulator based on ZnO nanoparticles

PROJECTION OF HOLOGRAMS FROM PHOTOREFRACTIVE OASLMs

Optimal liquid crystal modulation controlled by surface alignment and anchoring strength

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