Tunability of discrete diffraction in photonic liquid crystal fibres

2014 ◽  
Vol 22 (4) ◽  
Author(s):  
K. Rutkowska ◽  
U. Laudyn ◽  
P. Jung
Keyword(s):  
Liquid Crystal ◽  
Light Propagation ◽  
Optical Power ◽  
Experimental Tests ◽  
Experimental Conditions ◽  
Qualitative Comparison ◽  
External Temperature ◽  
Tuning Parameters ◽  
Gap Soliton ◽  
Discrete Diffraction

AbstractIn this paper theoretical and experimental results regarding discrete light propagation in photonic liquid crystal fibres (PLCFs) are presented. Particular interest is focused on tunability of the beam guidance obtained due to the variation in either external temperature or optical power (with assumption of thermal nonlinearity taking place in liquid crystals). Highly tunable (discrete) diffraction and thermal self-(de)focusing are studied and tested in experimental conditions. Specifically, spatial light localization and/or delocalization due to the change in tuning parameters are demonstrated, with possibility of discrete spatial (gap) soliton propagation in particular conditions. Results of numerical simulations (performed for the Gaussian beams of different widths and wavelengths) have been compared to those from experimental tests performed in the PLCFs of interest. Owning to the limit of experimental means, direct qualitative comparison was not quite accessible. Nevertheless, a qualitative agreement between theoretical and experimental data (obtained in analogous conditions) has been achieved, suggesting a compact and widely-accessible platform for the study of tunable linear (and nonlinear) discrete light propagation in two-dimensional systems. Proposed photonic structures are of a great potential for all-optical beam shaping and switching.

Light propagation mechanism switching in a liquid crystal infiltrated microstructured polymer optical fibre

2015 ◽  
Vol 23 (4) ◽  
Author(s):  
K.A. Rutkowska ◽  
K. Milenko ◽  
O. Chojnowska ◽  
R. Dąbrowski ◽  
T.R. Woliński
Keyword(s):  
Liquid Crystal ◽  
Optical Fibre ◽  
Total Internal Reflection ◽  
Light Propagation ◽  
Propagation Mechanism ◽  
External Temperature ◽  
Air Channels ◽  
Propagation Properties ◽  
Infiltration Method ◽  
Light Guidance

AbstractIn this work studies on propagation properties of a microstructured polymer optical fibre infiltrated with a nematic liquid crystal are presented. Specifically, the influence of an infiltration method on the LC molecular alignment inside fibre air-channels and, thus, on light guidance is discussed. Switching between propagation mechanisms, namely the transition from modified total internal reflection (mTIR) to the photonic bandgap effect obtained by varying external temperature is also demonstrated.

scholarly journals Design of Tunable Holographic Liquid Crystalline Diffraction Gratings

Sensors ◽  
2020 ◽  
Vol 20 (23) ◽  
pp. 6789
Author(s):  
Katarzyna A. Rutkowska ◽  
Anna Kozanecka-Szmigiel
Keyword(s):  
Liquid Crystal ◽  
Communication Networks ◽  
Optical Communication ◽  
Liquid Crystalline ◽  
Incident Light ◽  
Diffraction Gratings ◽  
Lagrange Equations ◽  
Experimental Conditions ◽  
Molecular Distribution ◽  
Polarization Gratings

Tunable diffraction gratings and phase filters are important functional devices in optical communication and sensing systems. Polarization gratings, in particular, capable of redirecting an incident light beam completely into the first diffraction orders may be successfully fabricated in liquid crystalline cells assembled from substrates coated with uniform transparent electrodes and orienting layers that force a specific molecular distribution. In this work, the diffraction properties of liquid crystal (LC) cells characterized by a continually rotating cycloidal director pattern at the cell substrates and in the bulk, are studied theoretically by solving a relevant set of the Euler-Lagrange equations. The electric tunability of the gratings is analyzed by estimating the changes in liquid crystalline molecular distribution and thus in effective birefringence, as a function of external voltage. To the best of our knowledge, such detailed numerical calculations have not been presented so far for liquid crystal polarization gratings showing a cycloidal director pattern. Our theoretical predictions may be easily achieved in experimental conditions when exploiting, for example, photo-orienting material, to induce a permanent LC alignment with high spatial resolution. The proposed design may be for example, used as a tunable passband filter with adjustable bandwidths, thus allowing for potential applications in optical spectroscopy, optical communication networks, remote sensing and beyond.

Study of Fraunhofer Diffraction Pattern from a Circular Aperture Using an Optical Fiber Microprobe

2011 ◽  
Vol 378-379 ◽  
pp. 565-568
Author(s):  
Wan Maisarah Mukhtar ◽  
P. Susthitha Menon ◽  
Sahbudin Shaari
Keyword(s):  
Optical Fiber ◽  
Diffraction Pattern ◽  
Light Propagation ◽  
Optical Power ◽  
Transverse Motion ◽  
Circular Aperture ◽  
Fraunhofer Diffraction ◽  
Fresnel Number ◽  
Function Profile ◽  
Effect Of Light

Fraunhofer diffraction pattern from a circular aperture with the diameter of 10µm was observed using an optical fiber microprobe. The optical fiber microprobe started to detect optical power when the distance between the probe and the circular aperture was more than 292µm. When the probe was moved in a lateral motion, the light propagation showed a Bessel function profile. When the optical fiber microprobe was moved from 293µm to 309µm from the centre of the circular aperture in a transverse motion, the power detected was not consistent with a continuation of maxima and minima due to the effect of light propagation from the circular aperture. We also observed that the distance between the probe and the centre of the circular aperture was directly proportional with the radius of focused spot and inversely proportional with the Fresnel number.

Waste Biomass from Marine Environment as Arsenic and Lead Biosorbent

2009 ◽  
Vol 71-73 ◽  
pp. 597-600 ◽  
Author(s):  
F. Beolchini ◽  
C. Pennesi ◽  
B. Testaferri ◽  
C. Totti ◽  
I. De Michelis ◽  
...  
Keyword(s):  
Marine Environment ◽  
Red Algae ◽  
Strong Dependence ◽  
Experimental Tests ◽  
Waste Biomass ◽  
Lead Uptake ◽  
Experimental Conditions ◽  
Arsenic Uptake ◽  
Metal Biosorption ◽  
Suspended Biomass

This paper deals with arsenic and lead biosorption by different waste biomasses coming from the marine environment. Shoreline seaweeds and seagrasses were used to adsorb metals from aqueous solutions, under different pH. Experimental tests were performed in order to study the equilibrium of biosorption with suspended biomass. The obtained results confirmed the possibility of using marine macrophyte biomass for heavy metal biosorption and evidenced a strong dependence of lead and arsenic uptake on the macrophyte structure. Brown algae were found to be the best sorbents for lead with a maximum observed lead uptake of 140 mg/g; green algae showed a maximum lead uptake in the range 50-70 mg/g; red algae were the worst lead sorbent, in the investigated experimental conditions, with a maximum lead uptake in the range 10-40 mg/g. As concerns arsenic, the macrophytes had in general good sorption abilities when compared with those of activated carbon. Furthermore red algae, that for lead were not effective, resulted to be the best sorbents for arsenic. This was explained by a different speciation in aqueous solution of lead (II), that is cationic with respect to arsenic(V), that is anionic.

scholarly journals Digital Twinning Process for Stirred Tank Reactors/Separation Unit Operations through Tandem Experimental/Computational Fluid Dynamics (CFD) Simulations

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1511
Author(s):  
Blaž Oblak ◽  
Simon Babnik ◽  
Vivian Erklavec-Zajec ◽  
Blaž Likozar ◽  
Andrej Pohar
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mixing Time ◽  
Tracer Tests ◽  
Flow Distribution ◽  
Experimental Tests ◽  
Cfd Simulations ◽  
Experimental Conditions ◽  
Separation Unit ◽  
Time Required

Computational fluid dynamics simulations (CFD) were used to evaluate mixing in baffled and unbaffled vessels. The Reynolds-averaged Navier−Stokes k–ε model was implemented in OpenFOAM for obtaining the fluid flow field. The 95% homogenization times were determined by tracer tests. Experimental tests were conducted by injecting sodium chloride into the vessel and measuring the conductivity with two conductivity probes, while the simulations replicated the experimental conditions with the calculation of the transport of species. It was found that the geometry of the system had a great effect on the mixing time, since the irregular flow distribution, which can be obtained with baffles, can lead to local stagnation zones, which will increase the time needed to achieve the homogenization of the solute. It was also found that measuring local, pointwise concentrations can lead to a high underestimation of the global mixing time required for the homogenization of the entire vessel. Dissolution of sucrose was also studied experimentally and by mathematical modeling. The dissolution of sucrose was found to be kinetically limited and a very good agreement was found between the experiments and the modeling approach. The extent of the applicability of CFD simulations was evaluated for enabling rapid process design via simulations.

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.

Analysis of light propagation mechanisms in photonic liquid crystal fibers

2006 ◽  
Author(s):  
Katarzyna Szaniawska ◽  
Tomasz Nasilowski ◽  
Tomasz R. Wolinski ◽  
Hugo Thienpont
Keyword(s):  
Liquid Crystal ◽  
Light Propagation ◽  
Crystal Fibers

Influence of the core size on light propagation in photonic liquid crystal fibers

2017 ◽  
Vol 25 (3) ◽  
pp. 198-204 ◽  
Author(s):  
M.M. Sala-Tefelska ◽  
S. Ertman ◽  
T.R. Woliński ◽  
P. Mergo
Keyword(s):  
Liquid Crystal ◽  
Light Propagation ◽  
Core Size ◽  
The Core ◽  
Crystal Fibers

Mathematical model of light propagation through liquid crystal display working under real conditions

2008 ◽  
Vol 16 (3) ◽  
Author(s):  
M. Olifierczuk
Keyword(s):  
Mathematical Model ◽  
Liquid Crystal ◽  
Light Propagation ◽  
Liquid Crystal Display ◽  
Spectral Characteristics ◽  
Contrast Ratio ◽  
Light Polarization ◽  
Optical Parameters ◽  
Complex Forms ◽  
Very High

AbstractThe main aim of our work is to present a theory of light propagation through a liquid crystal display worked out in our University. This theory takes into account real conditions of a display operation such as temporal coherence of light source, interference phenomena, spectral characteristics of refractive coefficients of individual layers and their complex forms, real directions of ordinary and extraordinary wavevectors into each layer, real directions of light polarization into anisotropic or dichroic layers etc. Therefore, our theory can be used to determine optical parameters of a liquid crystal display operating under real or at least quasi-real conditions. Contrary to other theories (e.g., Beremann or geometric optics approximation), this model is characterized by a small number of simplifications. Thus, it can be used to analyse a display operating in special conditions, such as military or out-door applications. In these cases, very high optical parameters (luminance and contrast ratio) aare needed. Application of even small simplifications conducts to significant changes of calculated parameters.

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