Optically activated shutter using a photo-tunable short-pitch chiral nematic liquid crystal

Morris, Stephen M.; Qasim, Malik M.; Cheng, Kuo-Hsing; Castles, Flynn; Ko, Doo Hyun; Gardiner, Damian J.; Nosheen, Sumaira; Wilkinson, Timothy D.; Coles, H. J.; Burgess, C.; Hill, Lawrence J.

doi:10.1063/1.4818679

Cited by 23 publications

(16 citation statements)

References 28 publications

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“…However, standing chiral helices with multidirectional orientations (tilted helical domains) on the surface of graphene demonstrates a unique prospect to fabricate devices with wide angle photonic structures (Figure 2). This in turn could help to devise optical filters based on diffused chiral nematic phase, including notch filters, colour reflectors, and light shutters 2,3,[24][25][26][27] At present, these laser sources can be used to produce relatively multi-modal light source as a result of the tilted helical domains in the vicinity of the graphene layers. A possible direct application of these laser sources could be a quick characterization of the quality of grown graphene by sampling the graphene domain-domain variation emission characteristics under coherent pumping of the LC medium (needs in-depth study, emission characteristics with known domain lattices).…”

Section: Discussionmentioning

confidence: 99%

“…There is considerable interest in the development of device applications using chiral nematic liquid crystals (LCs). These self-assembled, LC photonic band-gaps, demonstrate distinct, easily tuneable band edges [1][2][3] , which yield selective light reflections, allowing them to be used in device applications such as thermometers 4 , notch filters 5 and band-edge lasers 6-8 , to name a few applications. Band-edge organic lasers based upon chiral nematic LCs have stimulated significant research interest due to a remarkable combination of characteristics, such as ease of fabrication, single-mode emission, wide-band wavelength tunability, in micron-sized resonator structures where the thickness of the active film is less than the dimension of a human hair 6,9,10 .…”

Section: -Introductionmentioning

confidence: 99%

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Graphene and chiral nematic liquid crystals: a focus on lasing

et al. 2015

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Section: Discussionmentioning

confidence: 99%

Section: -Introductionmentioning

confidence: 99%

Graphene and chiral nematic liquid crystals: a focus on lasing

et al. 2015

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“…They present fast switching speeds and their materials properties can be easily tailored to suit the requirements of the optical systems. Moreover, the LC based shutters can also be tuned optically[ 6 ], where in the band gaps presented by the chiral nematic LCs can be tuned by an incident laser beam. Such a device is of potential importance for applications requiring remote switching involving the protection of sensor-based equipment from unwanted laser irradiation.…”

Section: Introductionmentioning

confidence: 99%

Laser additive manufacturing of 3D meshes for optical applications

et al. 2018

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Selective laser melting (SLM) is a widely used additive manufacturing process that can be used for printing of intricate three dimensional (3D) metallic structures. Here we demonstrate the fabrication of titanium alloy Ti–6Al–4V alloy based 3D meshes with nodally-connected diamond like unit cells, with lattice spacing varying from 400 to 1000 microns. A Concept Laser M2 system equipped with laser that has a wavelength of 1075 nm, a constant beam spot size of 50μm and maximum power of 400W was used to manufacture the 3D meshes. These meshes act as optical shutters / directional transmitters and display interesting optical properties. A detailed optical characterisation was carried out and it was found that these structures can be optimised to act as scalable rotational shutters with high efficiencies and as angle selective transmission screens for protection against unwanted and dangerous radiations. The efficiency of fabricated lattice structures can be increased by enlarging the meshing size.

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“…At the present time, the photo‐responsive liquid crystalline (LC) materials attract considerable attention due to their high potential application in the specific fields of optics, electronics, and photonics as polarization elements, light modulators or diffraction gratings for displays, laser devices, sensors, etc . One of the most promising types of such materials is cholesteric liquid crystals (CLC) that are characterized by a periodic helical supramolecular structure and high sensitivity to the external fields’ actions.…”

Section: Introductionmentioning

confidence: 99%

Electroinduced Diffraction Gratings in Cholesteric Polymer with Phototunable Helix Pitch

Ryabchun

Bobrovsky

Stumpe

et al. 2015

Advanced Optical Materials

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cholesteric mesophase is the selective light refl ection. The maximum refl ection wavelength is determined by the simple Equation ( 1) max nP λ =where n is the average refractive index of the material and P is the helix pitch. According to this relation, the variation of the helix pitch simultaneously changes the wavelength of light refl ection. The specifi c values of helix pitch depend on the chemical structure of the substances forming the cholesteric phase. In the most cases the cholesteric mesophase is formed by doping of nematic liquid crystals with a chiral additive (dopant) possessing a proper helical twisting power, β . This phenomenological parameter characterizes the ability of the dopant to twist the nematic structure according to Equation ( 2)where X is the concentration of the chiral dopant. This value strongly depends on the geometry of the chiral fragments and molecular interactions (steric, van der Waals, etc.) between the mixture components. These relations between chiral dopants structure and helical twisting power allowed one to create ways for phototuning of the helix pitch. [9][10][11] In many previously studied systems light exposure induces the photochemical E/Z isomerization of aromatic anisometric part of a chiral compound resulting in the formation of a bent-shaped Z-isomer having lower β-values compared to the initial rodlike E-isomer ( Figure 1 ).One of the most interesting and important areas of CLCs application is related to creation of the diffraction gratings. We can distinguish, at least, fi ve different ways to produce phase gratings in CLC systems. Let us briefl y describe each of them.1) The fi rst method is based on the application of the holographic technique to produce the volume phase gratings (refractive index modulation) and/or surface relief gratings (SRG) in photochromic (in most cases azobenzene-containing) cholesteric polymer systems. [12][13][14][15][16][17] In the majority instances the photosensitive moieties are mainly used for the photo-orientation or photo-induced mass transfer. However, there is an example of "dual" photo-recording consisting of For the fi rst time the cholesteric mixture containing nematic polymer with small amount of chiral-photochromic dopant is used for electroinduced diffraction gratings production. The gratings are obtained by applying electric fi eld to the planar-aligned cholesteric polymer layer causing its periodical distortion. Material developed permits manipulating supramolecular helical structure by means of UV exposure resulting in helix untwisting. Photo-controlling of helix pitch brings to change parameters of the electroinduced gratings. Due to macromolecular "nature" of the material one can easily stabilize electroinduced gratings by fast sample cooling. All-known cholesteric grating types are realized in the studied polymer material. It is observed that the grating vector can be oriented along or perpendicular to the rubbing direction of the cell. It is shown that the diffraction effi ciency is dictated by grating type and...

show abstract

Optically activated shutter using a photo-tunable short-pitch chiral nematic liquid crystal

Cited by 23 publications

References 28 publications

Graphene and chiral nematic liquid crystals: a focus on lasing

Graphene and chiral nematic liquid crystals: a focus on lasing

Laser additive manufacturing of 3D meshes for optical applications

Electroinduced Diffraction Gratings in Cholesteric Polymer with Phototunable Helix Pitch

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