Thin film polarizer and color filter based on photo-polymerizable nematic liquid crystal

Mohammadimasoudi, Mohammad; Neyts, Kristiaan; Beeckman, Jeroen

doi:10.1117/12.2079516

Cited by 3 publications

(2 citation statements)

References 17 publications

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“…26 It decreased by 0.09 with respect to the nominal 5CB birefringence (ne -no) = 0.19. The birefringence of monomer RM257 (with no = 1.508 and ne = 1.687) 27 and that of 5CB are of the same order and we don't expect the polymer birefringence to significantly modify the PSNLC one.…”

Section: Resultsmentioning

confidence: 87%

Liquid Crystal Films as Active Substrates for Nanoparticle Control

Gharbi

Palacio‐Betancur

Ayeb

et al. 2021

ACS Appl. Nano Mater.

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Organizing nanoparticles in a controlled way allows us to monitor their optical properties, in particular if it concerns metallic nanoparticles. It is particularly interesting to organize them on top of liquid crystal films to take advantage, in a second step, of the easy actuation of liquid crystals with external parameters like temperature, electric fields, etc…We show that despite their fluidity, nematic and smectic films allow formation of well-ordered hexagonal domains of gold spherical nanoparticles (AuNPs) at their surface but we also show that both nematic films and AuNP domains impact each other. Using Optical Microscopy, Atomic Force Microscopy (AFM), Scanning Electron microscopy (SEM), and Spectrophotometry, we compare nematic, polymer stabilized nematic and smectic films with AuNP domains made of NPs of diameter 6nm. On The liquid crystal films depressions are revealed below the AuNP domains whereas the AuNP domains appear well-organized but with a hexagonal period shortened with respect to AuNP monolayers formed on hard substrates. We interpret these features by the anchoring tilt imposed by the AuNP domains on the molecules. The smectic-A layers characteristic of the nematic surface transform into smectic-C layers which induce formation of depression. The energy penalty associated with the local smectic-A/smectic-C transition induces the shortening of the AuNP domain period in order to decrease the AuNP domain surface. The observed large depth of the polymer stabilized nematic depressions below AuNP domains may be explained either by an increased size of the polymer stabilized smectic layers close to the surface or by an increased number of polymer stabilized smectic liquid crystal smectic layers close to the surface with respect to pure nematic films.

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Section: Resultsmentioning

confidence: 87%

Liquid Crystal Films as Active Substrates for Nanoparticle Control

Gharbi

Palacio‐Betancur

Ayeb

et al. 2021

ACS Appl. Nano Mater.

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“…Nematic chiral liquid crystals (CLCs) are liquid crystalline materials with a helical symmetry [1]. The thickness corresponding to a full 2π rotation of the director is called the pitch P. The local optical axis in a liquid crystal (associated with the extra-ordinary refractive index) is parallel to the average orientation of the long axes of the molecules, which is denoted by the director L. The director of the liquid crystal remains parallel to the plane that is perpendicular to the helical axis, and the structure has a period of 0.5P.…”

Section: Introductionmentioning

confidence: 99%

Defect Modes Generated in a Stack of Spin-Coated Chiral Liquid Crystal Layers

Van Acker,

Lin,

Wang

et al. 2024

Crystals

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Nematic chiral liquid crystals (CLCs) are characterized by a helical arrangement of nematic LC molecules. A layer of CLC typically exhibits an optical reflection band due to Bragg reflection in the helical structure. When several layers of CLC are spin-coated and polymerized on top of each other without a barrier layer in between, defect modes can form in their reflection spectrum. By comparing experimental results and simulations, we investigate the origin of the defect modes, thereby revealing details on the behavior of the materials at the interfaces during deposition. Simulations show that these defect modes can originate from the migration of chiral dopant leading to a layer with a smaller pitch or from a discontinuity in the director orientation at the interface between two layers.

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Quantum dot lasing from a waterproof and stretchable polymer film

et al. 2022

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Colloidal quantum dots (QDs) are excellent optical gain materials that combine high material gain, a strong absorption of pump light, stability under strong light exposure and a suitability for solution-based processing. The integration of QDs in laser cavities that fully exploit the potential of these emerging optical materials remains, however, a challenge. In this work, we report on a vertical cavity surface emitting laser, which consists of a thin film of QDs embedded between two layers of polymerized chiral liquid crystal. Forward directed, circularly polarized defect mode lasing under nanosecond-pulsed excitation is demonstrated within the photonic band gap of the chiral liquid crystal. Stable and long-term narrow-linewidth lasing of an exfoliated free-standing, flexible film under water is obtained at room temperature. Moreover, we show that the lasing wavelength of this flexible cavity shifts under influence of pressure, strain or temperature. As such, the combination of solution processable and stable inorganic QDs with high chiral liquid crystal reflectivity and effective polymer encapsulation leads to a flexible device with long operational lifetime, that can be immersed in different protic solvents to act as a sensor.

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Thin film polarizer and color filter based on photo-polymerizable nematic liquid crystal

Cited by 3 publications

References 17 publications

Liquid Crystal Films as Active Substrates for Nanoparticle Control

Liquid Crystal Films as Active Substrates for Nanoparticle Control

Defect Modes Generated in a Stack of Spin-Coated Chiral Liquid Crystal Layers

Quantum dot lasing from a waterproof and stretchable polymer film

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