Optically Controlled Light Propagation in Dye-Doped Nematic Liquid Crystals with Homogeneous Alignment

2011 ◽  
Vol 497 ◽  
pp. 142-146
Author(s):  
Tomoyuki Sasaki ◽  
Kenta Miura ◽  
Hiroshi Ono ◽  
Osamu Hanaizumi
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Absorption Band ◽  
Temperature Variation ◽  
Light Propagation ◽  
Light Signal ◽  
Photothermal Effect ◽  
Absorption Of Light ◽  
Control Light

Light propagation in an optical waveguide fabricated by employing a dye-doped liquid crystal (DDLC) was observed. The propagation of a light signal in the waveguide was varied by irradiation with a control light whose wavelength was in the absorption band of the DDLC. By considering the photothermal effect of the DDLC, which enables the change of the refractive index due to temperature variation based on the absorption of light, we qualitatively explained the observed light propagation and demonstrated manipulation of the propagation.

Observation of Optical Soliton-Like Propagation in Dye-Doped Nematic Liquid Crystals with Homogeneous Alignment

2013 ◽  
Vol 596 ◽  
pp. 139-143 ◽  
Author(s):  
Tomoyuki Sasaki ◽  
Kenta Miura ◽  
Osamu Hanaizumi ◽  
Nobuhiro Kawatsuki ◽  
Hiroshi Ono
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Laser Beam ◽  
Light Propagation ◽  
Nematic Liquid Crystals ◽  
Incident Light ◽  
Absorption Peak ◽  
Photothermal Effect ◽  
Light Power ◽  
Polarization Azimuth

Nonlinear light propagation in a dye-doped liquid crystal (LC) was investigated experimentally. A laser beam with wavelength far from the absorption peak of the material was coupled into an LC cell with homogeneous alignment, and the propagation in the cell was observed. When the polarization azimuth of the incident light was orthogonal to the orientation direction of the LC, soliton-like propagation was obtained for milliwatts of light power in spite of the low absorption. We clarified that the observed nonlinearity is due principally to the photothermal effect enhanced by the dye.

scholarly journals Tunable Channel Drop Filter in a Two-Dimensional Photonic Crystal Modulated by a Nematic Liquid Crystal

2006 ◽  
Vol 2006 ◽  
pp. 1-6 ◽  
Author(s):  
Chen-Yang Liu ◽  
Lien-Wen Chen
Keyword(s):  
Liquid Crystals ◽  
Integrated Circuits ◽  
Wavelength Division Multiplexing ◽  
Light Propagation ◽  
Nematic Liquid Crystals ◽  
Fdtd Method ◽  
Wavelength Division ◽  
Resonance Frequencies ◽  
Potential Applications ◽  
Control Light

Photonic crystals (PCs) have many potential applications because of their ability to control light-wave propagation and because PC-based waveguides may be integrated into optical circuits. We propose a novel tunable PC channel drop filter based on nematic liquid crystals and investigate its properties numerically by using the finite-difference time-domain (FDTD) method. The refractive indices of liquid crystals can be actively modulated after infiltrating nematic liquid crystals into the microcavity in PC waveguides with square lattices. Then we can control light propagation in a PC waveguide. We analyze theQ-factors and resonance frequencies of a tunable PC channel drop filter by considering various indices modulation of liquid crystals. The novel component can be used as wavelength division multiplexing in photonic integrated circuits.

Tunable properties of light propagation in photonic liquid crystal fibers

2006 ◽  
Vol 14 (4) ◽  
Author(s):  
K. Szaniawska ◽  
T. Nasilowski ◽  
T. Woliński ◽  
H. Thienpont
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Propagation ◽  
Solid Core ◽  
Simulation Methods ◽  
Pure Silica ◽  
Tunable Properties ◽  
Crystal Fibers ◽  
Propagation Properties ◽  
Good Agreement

AbstractTunable properties of light propagation in photonic crystal fibers filled with liquid crystals, called photonic liquid crystal fibers (PLCFs) are presented. The propagation properties of PLCFs strongly depend on contrast between refractive indices of the solid core (pure silica glass) and liquid crystals (LCs) filing the holes of the fiber. Due to relatively strong thermo-optical effect, we can change the refractive index of the LC by changing its temperature. Numerical analysis of light propagation in PLCF, based on two simulation methods, such as finite difference (FD) and multipole method (MM) is presented. The numerical results obtained are in good agreement with our earlier experimental results presented elsewhere [1].

Active Photonic Crystals Based multiplexer

2006 ◽  
Vol 934 ◽  
Author(s):  
Principia Dardano ◽  
Vito Mocella ◽  
Luigi Sirleto ◽  
Luigi Moretti ◽  
Ivo Rendina
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Photonic Crystal ◽  
Photonic Crystals ◽  
Square Lattice ◽  
Two Dimensional ◽  
Optical Effect ◽  
Electro Optical Effect ◽  
Silicon Rods

ABSTRACTIn the last years, in order to achieve active tuning of photonic crystals devices, the possibility to use liquid crystal inside photonic crystals has been explored.On this line of argument, in this paper, we numerically investigate a tunable T-shaped waveguide diplexer, based on a two-dimensional square lattice photonic crystal composed of silicon rods in a liquid crystals. We prove that complete splitting of the entire input wavelengths range in two sub-ranges symmetrical with respect to the middle (switching) wavelength, and propagating in right and left arms respectively, can be achieved. Moreover, changing the refractive index of liquid crystals by electro-optical effect, a tuning of switching wavelength of about 60 nm can be obtained.

scholarly journals Enhancement of the SPR Effect in an Optical Fiber Device Utilizing a Thin Ag Layer and a 3092A Liquid Crystal Mixture

Molecules ◽  
2021 ◽  
Vol 26 (24) ◽  
pp. 7553
Author(s):  
Joanna Korec ◽  
Karol A. Stasiewicz ◽  
Katarzyna Garbat ◽  
Leszek R. Jaroszewicz
Keyword(s):  
Refractive Index ◽  
Surface Plasmon Resonance ◽  
Liquid Crystal ◽  
Optical Fiber ◽  
Surface Plasmon ◽  
Light Propagation ◽  
Resonance Effect ◽  
Surface Plasmon Resonance Effect ◽  
Tapered Optical Fiber ◽  
Crystal Cells

This paper is a continuation of previous work and shows the enhancement of the surface plasmon resonance effect in a tapered optical fiber device. The study investigated liquid crystal cells containing a tapered optical fiber covered with a silver nanolayer, surrounded by a low refractive index liquid crystal in terms of the properties of light propagation in the taper structure. Silver films with a thickness of d = 10 nm were deposited on the tapered waist area. Measurements were performed at room temperature; liquid crystal steering voltage U from 0 to 200 V, with and without any amplitude modulation with a frequency of f = 5 Hz, and the wavelength λ ranged from 550 to 1200 nm. A significant influence of the initial arrangement of liquid crystals molecules on light propagation was observed. Three types of liquid crystal cells—orthogonal, parallel, and twist—were considered. During the measurements, resonant peaks were obtained—the position of which can also be controlled by the type of liquid crystal cells and the steering voltage. Based on the obtained results, the best parameters, such as highest peak’s width reduction, and the highest SNR value were received for twisted cells. In addition, the present work was compared with the previous work and showed the possibility of improving properties of the manufactured probes, and consequently, the surface plasmon resonance effect. In the presented paper, the novelty is mainly focused on the used materials as well as suitable changes in applied technological parameters. In contrast to gold, silver is characterized by different optic and dielectric properties, e.g., refractive index, extension coefficient, and permittivity, which results in changes in the light propagation and the SPR wavelengths.

scholarly journals Optically-driven switching of a planar nematic liquid crystal cell with parallel rubbing

2017 ◽  
Vol 9 (2) ◽  
pp. 39
Author(s):  
Varsenik Nersesyan
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Tilt Angle ◽  
Light Propagation ◽  
Domain Walls ◽  
Optical Field ◽  
Liquid Crystal Cell ◽  
Crystal Cell ◽  
Order Of Magnitude

This letter reports on the switching of a planar nematic liquid crystal cell with parallel rubbing of the alignment layers, under the application of a voltage, when there is initially an optical field. The voltage application over the liquid crystal in such a cell leads normally to the formation of multiple domains because there is the two switching directions are equivalent. However, an incident optical field under an angle will locally reorient the director and break the symmetry between the equivalent switching directions. The subsequent application of a voltage pulse amplifies the tilt angle and leads to the formation of a dominant domain, with an order of magnitude larger size than the optical beam profile. Several switching conditions are demonstrated for different incident angles of the beam. It is shown that the final switching direction of the entire cell is determined by the tilt angle of the optical field. The lensing effects due to the modified director distribution in the domain walls is analyzed qualitatively. Full Text: PDF ReferencesI. C. Khoo, Liquid crystals (2nd ed. Hoboken (NJ), Wiley, 2007) CrossRef A. Zolotko, V. Kitaeva, N. Kroo et al. OCBP. JETP Lett. 32, 158?162 (1980). DirectLink J. Beeckman, K. Neyts, X. Hutsebaut X, et al. "Simulations and experiments on self-focusing conditions in nematic liquid-crystal planar cells", Opt Express, 12, 1011? 1018 (2004). CrossRef M. Peccianti, C. Conti, G. Assanto, et al. "Electrically assisted self-confinement and waveguiding in planar nematic liquid crystal cells", Appl. Phys. Lett. 77, 7 ? 9 (2000). CrossRef N. Kravets, A. Piccardi, A. Alberucci et al, "Bistability with Optical Beams Propagating in a Reorientational Medium", Phys. Rev. Lett. 113, 023901 (2014) CrossRef A. Piccardi, N. Kravets, A. Alberucci et al, "Voltage-driven beam bistability in a reorientational uniaxial dielectric", APL Photonics 1, 011302 (2016). CrossRef V. Nersesyan, T. Brans, F. Beunis, R. Drampyan , J. Beeckman, K. Neyts, "Light-controlled reorientation of nematic liquid crystal driven by an electric field", Liquid crystals, 43, 1422-1430 (2016). CrossRef J. Beeckman, K. Neyts, W. Cort, et al. "Non-linear light propagation and bistability in nematic liquid crystals", Proc SPIE 7414, 74140K (2009). CrossRef

Polymer-Dispersed Liquid Crystals: Boojums at Work

MRS Bulletin ◽  
1991 ◽  
Vol 16 (1) ◽  
pp. 22-28 ◽  
Author(s):  
J. William Doane
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Polarized Light ◽  
Solid Particles ◽  
Water Soluble ◽  
The Other ◽  
Polymer Materials ◽  
Water Soluble Polymer ◽  
Polymer Dispersed

The idea of dispersing micron-size birefringent particles in a polymer to selectively scatter light is not new. In the 1930s Land patented a light polarizing material in which small, oriented solid crystallites were suspended in a clear polymer. The polymer material was selected so that its refractive index matched one of the principal refractive indices of the crystallites while the other did not. The resuit was a light polarizer tha t would pass one component of polarized light but scatter the other component out of the beam path.This idea was substantially expanded by the introduction of liquid crystals as the birefringent material. The orientation of the particles (in this case droplets), and hence the refractive index match and the scattering, could be controlled by an electric field. Such a material could be used as a light shutter for either unpolarized or polarized light. In the mid-1970s this basic concept was applied by Hilsum, but having no way to disperse droplets of liquid crystals in a polymer, he did the opposite and put optically isotropic solid particles in the birefringent liquid crystal.Although Hilsum demonstrated the concept, no commercial device was produced, probably because the shutter contrast was limited. Since then several ways have been found to disperse droplets in a polymer: filling the pores of a microfilter; emulsifying the liquid crystal in a water soluble polymer; and using phase separation methods to create a dispersion of droplets in non-aqueous polymer materials.

Infrared Microscopic Imaging of the Diffusion of Liquid Crystals into Thermoplastics

1997 ◽  
Vol 3 (S2) ◽  
pp. 841-842
Author(s):  
Bentley G. Wall ◽  
Chris M. Snively ◽  
Jack L. Koenig
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Polymer Matrix ◽  
Thermoplastic Polymer ◽  
General Direction ◽  
Display Devices ◽  
Polymer Dispersed

Thermoplastic polymer/liquid crystal systems have found application in the generation of display devices known as thermoplastic, polymer dispersed liquid crystals (PDLCs). These systems take advantage of the beneficial properties of both components to generate a device that has unique optical properties. The liquid crystal is dielectric and responds to an electric field. The polymer confines the liquid crystal so that the cells are closed. The two components are melted together until they are miscible. At lower temperatures, the two components phase separate. The liquid crystal component is the minor phase and takes the form of many tiny droplets contained within the major-phase, polymer matrix. An application of an electric field across these systems causes the liquid crystal within the droplets to align with the field. The systems are engineered such that when this alignment occurs there is no refractive index difference between the liquid crystal in the droplets and the polymer matrix, thus, the cells appear optically transparent. When there is no field applied, the liquid crystals in each droplet are aligned without respect to a general direction according to the surface energetics of each droplet/polymer interface. When this is the case, there is a refractive index mismatch between the droplets and the polymer and the cells are opaque. Research of these systems is aimed at improving the optical properties in order to facilitate the manufacturing of improved devices utilizing this technology. Because these systems are generated by a diffusion-controlled, phase separation process, understanding the relevant parameters, particularly the diffusion coefficients, should enable the manufacturing processes of these systems to be controlled more efficiently, generating improved optical properties.

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