Variable pitch hydrodynamic electro-optic gratings utilising bent liquid crystal dimers

Morris, Rowan; Jones, John C.; Nagaraj, Mamatha

doi:10.1039/d0sm01425g

Cited by 5 publications

(3 citation statements)

References 110 publications

(232 reference statements)

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“…Here, the maximum value η m ̸ = 0 of 33.9% occurs for the m = ±1 diffractive orders when ϕ max = 3.68. The most studied hydrodynamic NLC DOEs are created by electro-convection [24,[27][28][29][30][31][32]. These are instabilities caused by ion movement through the material induced by external electric fields [18,19,[33][34][35].…”

Section: Instabilities In Nlcs As Diffraction Gratingsmentioning

confidence: 99%

Inducing variable pitch gratings in nematic liquid crystals using chirped surface acoustic wave transducers

Morris

Jones

Nagaraj

2022

J. Phys. D: Appl. Phys.

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Inducing hydrodynamic flow in nematic liquid crystals (NLCs) reorients the symmetry axis of the material- the director, causing changes in the optical properties. The resulting optical gratings have potential use as switchable diffractive optical elements (DOEs). In this study, surface acoustic waves (SAWs) are applied to an NLC device to induce periodic vortices through hydrodynamic instabilities. We show a linear relationship between the wavelength of the applied SAW and induced grating period, where the coefficient is determined by the ratio of the speed of sound in the substrate to that in the nematic liquid crystal. This relationship is further used to design a novel device, where the period of the hydrodynamic grating can be continuously varied from 90 μm to 260 μm by utilising a broadband (chirped) SAW transducer. These devices present great potential for creating a new class of continuously variable DOEs, overcoming current technological limitations.

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Section: Instabilities In Nlcs As Diffraction Gratingsmentioning

confidence: 99%

Inducing variable pitch gratings in nematic liquid crystals using chirped surface acoustic wave transducers

Morris

Jones

Nagaraj

2022

J. Phys. D: Appl. Phys.

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“…One such is the Normal Roll (NR) texture caused by the director undulating to form an approximately 1D diffraction grating with Λ grat of order d [15,174]. Depending on the frequency, the value Λ grat can typically vary by a factor of two continuously [171,172,[175][176][177]. This typically allows wide-angle lowefficiency steering as the theoretical maximum η m=1 is around 40% without blazing, and significant optical losses occur within the devices.…”

Section: Flow-induced Patternsmentioning

confidence: 99%

Liquid Crystal Devices for Beam Steering Applications

2021

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Liquid crystals are valuable materials for applications in beam steering devices. In this paper, an overview of the use of liquid crystals in the field of adaptive optics specifically for beam steering and lensing devices is presented. The paper introduces the properties of liquid crystals that have made them useful in this field followed by a more detailed discussion of specific liquid crystal devices that act as switchable optical components of refractive and diffractive types. The relative advantages and disadvantages of the different devices and techniques are summarised.

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“…Using EC, with a proper combination of the amplitude and frequency of the applied ac voltage, the direction of the wave vector and to some extent also its magnitude can be adjusted. It has been shown that by adding SBCN1 to the ionic-saltdoped, commercial nematic mixture MLC 2081, the range in which the wave number can be tuned by the frequency of the applied voltage could be substantially extended, both towards lower and higher q values [121]. This improvement has been attributed to the change of the elastic moduli (especially to the reduction of K3) occurring as a consequence of doping with the soft-core BCN.…”

Section: Periodic Patterns As Gratings For Optical Devicesmentioning

confidence: 99%

Electrically driven structures in bent-core nematics

2021

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This review, dedicated to the memory of B. K. Sadashiva, concerns electrically driven patterns and defects in bent core nematics (BCNs) made of hard-core, soft-core or bent-rod type of molecules. It covers (a) spatially periodic patterns associated with electroconvection and flexoelectric deformation, (b) dislocations in these patterned states and (c) various types of defects induced essentially in homogeneous, unpatterned states of BCNs. While in general, the wealth of pattern morphologies is just as rich in BCNs as in rod-like nematics, certain features of electroconvection have so far been observed only in some BCN materials. Some attributes relating to the generation and behaviour of defects in electric field may also be ascribed to material properties specific to BCNs. It is also shown that the electric field induced patterns as well as their modification by light irradiation may serve as optical gratings and thus establishes the background for designing new photonic devices.

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Variable pitch hydrodynamic electro-optic gratings utilising bent liquid crystal dimers

Abstract: Electrohydrodynamic Instabilities in nematic liquid crystals cause uniform and continuously variable pitch diffraction gratings. Liquid crystal dimers allow greater range of elastic constants, allowing wider angle diffraction to be achieved.

Cited by 5 publications

References 110 publications

Inducing variable pitch gratings in nematic liquid crystals using chirped surface acoustic wave transducers

Inducing variable pitch gratings in nematic liquid crystals using chirped surface acoustic wave transducers

Liquid Crystal Devices for Beam Steering Applications

Electrically driven structures in bent-core nematics

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