scholarly journals Photo-Aligned Nematic Liquid Crystals Enable the Modulation of Thermoplasmonic Heating

2021 ◽  
Vol 11 (14) ◽  
pp. 6272
Author(s):  
Giovanna Palermo ◽  
Rossella Grillo ◽  
Luigia Pezzi ◽  
Thomas Bürgi ◽  
Nelson Tabiryan ◽  
...  
Keyword(s):  
Thin Film ◽  
Gold Nanoparticles ◽  
Refractive Index ◽  
Liquid Crystal ◽  
Single Layer ◽  
Organic Layer ◽  
Molecular Reorientation ◽  
Index Value ◽  
Director Reorientation ◽  
Director Orientation

We experimentally demonstrate that the plasmonic heat delivered by a single layer of homogeneously distributed gold nanoparticles (AuNPs), immobilized on a glass substrate, can be optically tuned by taking advantage of the properties of an organic layer based on azobenzene and nematic liquid crystal (NLC) molecules. The effect, which exploits the dependence of the NLC refractive index value on the molecular director orientation, is realized using the polarization-dependent, light-induced molecular reorientation of a thin film of photo-aligning material that the NLC is in contact with. The reversibility of the optically induced molecular director reorientation of the NLC enables an active modulation of the plasmonic photo-induced heat.

Investigation on Optical Properties of Transparent ITO Thin Films

2011 ◽  
Vol 347-353 ◽  
pp. 3481-3484
Author(s):  
Xue Hua Li ◽  
Dong Sheng Wang ◽  
Jian Zhou Du
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Refractive Index ◽  
Optical Properties ◽  
Glass Substrate ◽  
Film Theory ◽  
Single Layer ◽  
Minimum Value ◽  
Ito Thin Films ◽  
Layer Thin Film

Based on the single-layer thin film theory, we calculated transmittance of ITO thin film. The reflectivity arrive a maximum or a minimum according to whether the refractive index of film is greater or smaller than the refractive index of the glass substrate. we obtain the same maximum of transparence which is above 95% and the minimum value which decrease to 76.5% with the increase of refractive index.

scholarly journals Research on Optical Properties of Tapered Optical Fibers with Liquid Crystal Cladding Doped with Gold Nanoparticles

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 306 ◽  
Author(s):  
Joanna E. Moś ◽  
Joanna Korec ◽  
Karol A. Stasiewicz ◽  
Bartłomiej Jankiewicz ◽  
Bartosz Bartosewicz ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Liquid Crystal ◽  
Optical Fibers ◽  
Surrounding Medium ◽  
Environmental Parameters ◽  
Different Temperatures ◽  
Properties Of Materials ◽  
Time Courses ◽  
Materials Used ◽  
Index Value

This paper presents results obtained for biconical tapered fibers surrounded/immersed in liquid crystal mixtures. The phenomenon of light propagating in the whole structure of a tapered fiber allows the creation of a sensor where the tapered region represents a core whereas the surrounding medium becomes a cladding. Created devices are very sensitive to changing refractive index value in a surrounding medium caused by modifying external environmental parameters like temperature, electric or magnetic field. For this reason, the properties of materials used as cladding should be easily modified. In this investigation, cells have been filled with two different nematic liquid crystals given as 1550* and 6CHBT (4-(trans-4-n-hexylcyclohexyl) isothiocyanatobenzoate), as well as with the same mixtures doped with 0.1 wt% gold nanoparticles (AuNPs). Optical spectrum analysis for the wavelength range of 550–1150 nm and time-courses performed for a wavelength of 846 nm at the temperature range of T = 25–40 °C were provided. For all investigations, a steering voltage in the range of 0–200 V which allows establishing the dopes’ influence on transmitted power and time response at different temperatures was applied.

Influence of temperature diffusion on molecular reorientation in nematic liquid crystals

2018 ◽  
Vol 27 (01) ◽  
pp. 1850011 ◽  
Author(s):  
Filip A. Sala ◽  
Marzena M. Sala-Tefelska ◽  
Maksymilian J. Bujok
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Thermal Effects ◽  
Rate Of Change ◽  
Heat Diffusion ◽  
Molecular Reorientation ◽  
Heat Diffusion Equation ◽  
Extraordinary Refractive Index ◽  
Elastic Coefficients

In this paper, the theoretical analyses of optically induced molecular reorientation are presented in a nematic liquid crystal cell. Due to the absorption of the light beam, the temperature of the cell increases, which induces change of anisotropy and the Frank elastic coefficients. In our analyses, a simple model is used. It is based on the Frank–Oseen elastic theory to describe molecular reorientation and on a heat diffusion equation to model thermal effects. Molecular reorientation, its width and maximum value, and extraordinary refractive index are analyzed versus various values of absorption coefficient, rate of change of elastic coefficient, and thermal conductance. It appears that thermal effects do not influence the width of the molecular reorientation. The nonlocality is nearly unaffected by the increase of temperature. However, the maximum molecular reorientation might increase with temperature, in most cases, the extraordinary refractive index decreases with temperature. Only for unlikely high rates of change of elastic coefficients, the refractive index increases with temperature. Moreover, the transition between liquid crystal and isotropic phases is also discussed. The range of input beam width for which the material lasts in a liquid crystal state is also presented. Simulations are performed for parameters corresponding to two liquid crystals: low birefringent 1550 and 6CHBT of a medium birefringence.

scholarly journals Two helices from one chiral centre – self organization of disc shaped chiral nanoparticles

2021 ◽  
Author(s):  
Huanan Yu ◽  
Wentao Qu ◽  
Feng Liu ◽  
Georg H. Mehl
Keyword(s):  
Gold Nanoparticles ◽  
Liquid Crystal ◽  
Self Organization ◽  
Helix Formation ◽  
Chiral Nematic

Gold nanoparticles (NPs) were surface functionalized with hexanethiol groups and chiral nematic discogen ligands. A superlattice, liquid crystal behaviour and helix formation of the discs and a second helical organisation of the NPs were detected.

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