Highly dispersive liquid crystal diffraction gratings with continuously varying periodicity

Nys, Inge; Ropač, Peter; Berteloot, Brecht; Ravnik, Miha; Neyts, Kristiaan

doi:10.1016/j.molliq.2023.122062

Cited by 6 publications

(6 citation statements)

References 38 publications

(65 reference statements)

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“…We have demonstrated that this mechanism to avoid a twist conflict by introducing an out-of-plane tilt of the director, can also be used in more general conditions to design non-periodic topological entities with a localized out-ofplane director orientation [18,19]. Apart from that, we have studied the electrical switching behavior of these gratings in detail, and also varied the surface anchoring patterns to produce highly dispersive gratings [14]. Photoalignment patterning with the SLM setup allows to vary the periodicity of the surface anchoring pattern and in this way induce splitting of the diffraction orders.…”

Section: Transmissive Devices With Non-chiral or Weakly Chiral Lcmentioning

confidence: 99%

“…Taking advantage of the versatility of the photoalignment technique, we have demonstrated different LC based geometric phase optical component, either working in transmission or reflection [5][6][7][8][9][10][11][12][13][14][15][16]. As discussed in section 2, we used nonchiral or chiral LC with a long pitch to demonstrate transmissive devices with 1D or 2D diffraction patterns.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Diffractive optical elements based on photoaligned liquid crystals: reflective and transmissive devices with different functionalities

Nys,

Stebryté,

Sharma

et al. 2024

Liquid Crystals Optics and Photonic Devices

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Diffractive optical elements (DOEs) are increasingly used as miniaturized and lightweight components in photonic devices. Efficient steering of light can be obtained with the help of photoaligned liquid crystal (LC) devices that modulate the geometric phase of light. We study a multitude of diffractive LC structures, ranging from simple one-dimensional gratings with a periodically rotating surface alignment, to highly dispersive gratings, multi-stable gratings and different types of lenses. All these components are enabled by photoalignment technology, that allows to control the geometric phase of the transmitted or reflected light by locally varying the azimuthal anchoring direction of the LC. Next to the standard nematic LCs, we also investigate the use of chiral nematic LCs (with different chiral pitches) and dual-frequency nematic LCs. The use of short pitch chiral LC gives rise to highly efficient diffraction in reflective devices, as we have demonstrated in linear gratings and on- and off-axis lenses. Dual-frequency LC on the other hand allows to substantially enhance the diffraction efficiency over large angles in transmissive devices. Imposing well-designed anchoring patterns at the substrates also allows to obtain highly dispersive configurations or structures with hysteresis switching as a function of the applied electric field. In all case, the working principles of the component can be understood with the help of finite element Q-tensor simulations for the LC director.

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Section: Transmissive Devices With Non-chiral or Weakly Chiral Lcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Diffractive optical elements based on photoaligned liquid crystals: reflective and transmissive devices with different functionalities

Nys,

Stebryté,

Sharma

et al. 2024

Liquid Crystals Optics and Photonic Devices

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“…Diverse optical devices have been realized by combining curable LC materials on the photoalignment layer. Examples include patterned birefringent films and polarized diffraction devices. ,− Alternatively, photoalignable LC polymers (PLCPs) form their own molecularly oriented structure via LP light exposure. The LP light exposure is often followed by thermal stimulation. − ,, Several types of PLCPs have been developed.…”

Section: Introductionmentioning

confidence: 99%

“…Photoalignment has been investigated to fabricate liquid crystal (LC) displays, − holography and optical films, − and polarization sensitive diffraction devices. − Thin photosensitive polymeric films, which include azobenzene or photo-cross-linkable moieties, are frequently applied to the photoalignment layer using linearly polarized (LP) light exposure. These films produce a very small birefringence (Δ n ) via an axis-selective photoreaction employing LP light when molecular reorientation does not occur …”

Section: Introductionmentioning

confidence: 99%

Birefringence and Orientation Direction Control of Photoalignable Liquid Crystalline Copolymer Films Based on In Situ Modification of Mesogenic Groups

Uemura,

Nakajima,

Marui

et al. 2024

Langmuir

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Controlling the birefringence of optical films is imperative to fabricate thin birefringent optical devices. Here, new photoalignable liquid crystalline copolymers (PLCPs) with 4formylphneyl benzoate (PA) and cinnamic acid (CA) side groups are synthesized, which attain high photoreactivity and controllability of the orientation direction. Additionally, the exposed films are treated with 2-aminofluorene (AF) for an in situ condensation of PA with AF to form a Schiff base with a high inherent birefringence. Birefringence of the photoaligned film can be controlled up to 0.45 without disturbing the photoinduced orientation structure.

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“…Along with well-known display applications, liquid crystals (LCs) are of great interest for various photonic devices. These are electrically controlled beam-steering devices and switched gratings [1,2], lenses and arrays of high-aperture lenses [3][4][5][6][7], liquid crystal metasurfaces [8][9][10], as well as liquid crystal light amplifiers and microlasers [11][12][13][14][15][16]. In many cases, the operation of these devices presupposes an effective waveguide mode of light propagation.…”

Section: Introductionmentioning

confidence: 99%

Waveguide Properties of Homogeneously Aligned Liquid Crystal Layers between ITO Electrodes and Thin Alignment Films

Palto,

Geivandov

2023

Photonics

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Numerical studies of the waveguide properties of liquid crystal layers bounded by substrates with indium tin oxide (ITO) electrodes using the finite difference time-domain (FDTD) method are carried out. On the basis of the experimental transmittance spectra of ITO-coated glass substrates in the visible and near-infrared ranges, a Lorentz model describing the dielectric properties of the ITO electrodes is created. Then, by numerical modeling, optical systems including a homogeneously aligned LC layer between the thin alignment films and the ITO electrodes on the quartz substrates are studied. It is shown that, in the case of the use of traditional alignment films or their absence, the ITO electrodes lead to significant resonant losses in the waveguide mode for both TE- and TM-polarized light. The losses mechanism based on a phase-synchronized mode coupling occurring in relatively narrow spectral ranges is discussed. We also propose a method to control and exclude the losses using thin alignment films with a proper thickness and low refractive index.

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Highly dispersive liquid crystal diffraction gratings with continuously varying periodicity

Cited by 6 publications

References 38 publications

Diffractive optical elements based on photoaligned liquid crystals: reflective and transmissive devices with different functionalities

Diffractive optical elements based on photoaligned liquid crystals: reflective and transmissive devices with different functionalities

Birefringence and Orientation Direction Control of Photoalignable Liquid Crystalline Copolymer Films Based on In Situ Modification of Mesogenic Groups

Waveguide Properties of Homogeneously Aligned Liquid Crystal Layers between ITO Electrodes and Thin Alignment Films

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