scholarly journals Hybrid photosensitive structures based on nematic liquid crystals and lithium niobate substrates

2018 ◽  
Vol 4 (1) ◽  
pp. 14-21 ◽  
Author(s):  
Liana Lucchetti ◽  
Victor Reshetnyak
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Lithium Niobate ◽  
Nonlinear Optical ◽  
Photovoltaic Effect ◽  
Hybrid Structures ◽  
Liquid Crystal Films ◽  
Self Assembling ◽  
Crystal Films ◽  
Crystal Cells

Abstract Liquid crystal cells based on lithium niobate substrates have recently been proposed as good candidates for optofluidic devices and for light-induced controlled generation of defects in liquid crystal films. The peculiarity of these structures lies in the possibility of using the bulk photovoltaic effect of lithium niobate to obtain an optically induced dc field able to affect the molecular liquid crystal director. Reversible fragmentation and self-assembling of liquid crystal droplets driven by the lithium niobate pyroelectric properties have also been reported. We review the basic results obtained so far with the aim of making the point and seeing what else can be done in the framework of the realization of hybrid structures combining lithium niobate with the electro-optical and nonlinear optical properties of liquid crystals.

scholarly journals Optofluidic Platform Based on Liquid Crystals in X-Cut Lithium Niobate: Thresholdless All-Optical Response

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 908
Author(s):  
Fabrizio Ciciulla ◽  
Annamaria Zaltron ◽  
Riccardo Zamboni ◽  
Cinzia Sada ◽  
Francesco Simoni ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Lithium Niobate ◽  
Photovoltaic Effect ◽  
Optical Control ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Threshold Behaviour ◽  
All Optical

In this study, we present a new configuration of the recently reported optofluidic platform exploiting liquid crystals reorientation in lithium niobate channels. In order to avoid the threshold behaviour observed in the optical control of the device, we propose microchannels realized in a x-cut crystal closed by a z-cut crystal on the top. In this way, the light-induced photovoltaic field is not uniform inside the liquid crystal layer and therefore the conditions for a thresholdless reorientation are realized. We performed simulations of the photovoltaic effect based on the well assessed model for Lithium Niobate, showing that not uniform orientation and value of the field should be expected inside the microchannel. In agreement with the re-orientational properties of nematic liquid crystals, experimental data confirm the expected thresholdless behaviour. The observed liquid crystal response exhibits two different regimes and the response time shows an unusual dependence on light intensity, both features indicating the presence of additional photo-induced fields appearing above a light intensity of 107 W/m2.

scholarly journals Functional Smart Dispersed Liquid Crystals for Nano- and Biophotonic Applications: Nanoparticles-Assisted Optical Bioimaging

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
N. V. Kamanina ◽  
S. V. Likhomanova ◽  
Yu. A. Zubtcova ◽  
A. A. Kamanin ◽  
A. Pawlicka
Keyword(s):  
Carbon Nanotubes ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Solid Substrate ◽  
Holographic Recording ◽  
Self Assembling ◽  
Aligned Carbon Nanotubes ◽  
Vertically Aligned ◽  
Crystal Cells ◽  
Modified Functional

Functional nematic liquid crystal structures doped with nano- and bioobjects have been investigated. The self-assembling features and the photorefractive parameters of the structured liquid crystals have been comparatively studied via microscopy and laser techniques. Fullerene, quantum dots, carbon nanotubes, DNA, and erythrocytes have been considered as the effective nano- and biosensitizers of the LC mesophase. The holographic recording technique based on four-wave mixing of the laser beams has been used to investigate the laser-induced change of the refractive index in the nano- and bioobjects-doped liquid crystal cells. The special accent has been given to novel nanostructured relief with vertically aligned carbon nanotubes at the interface: solid substrate-liquid crystal mesophase. It has been shown that this nanostructured relief influences the orienting ability of the liquid crystal molecules with good advantage. As a result, it provokes the orientation of the DNA. The modified functional liquid crystal materials have been proposed as the perspective systems for both the photonics and biology as well as the medical applications.

A Squeegee Coating Apparatus for Producing a Liquid Crystal Based Bio-Transducer

2013 ◽  
Vol 465-466 ◽  
pp. 759-763
Author(s):  
Chin Fhong Soon ◽  
Zai Peng Goh ◽  
Lee Chin Ku ◽  
Ten Ten Lee ◽  
Kian Sek Tee
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Single Cells ◽  
Petri Dish ◽  
Angular Speed ◽  
Liquid Crystal Films ◽  
Crystal Substrate ◽  
Crystal Films ◽  
A Cell ◽  
Petri Dishes

Cholesteryl ester liquid crystals were discovered with a new application in sensing traction forces of single cells. The liquid crystal bio-transducer is produced by manual scraping of liquid crystals onto the petri dish, in which the technique is highly subjective to the skill of the user to produce homogeneously spread liquid crystal substrates. This paper describes the development of an apparatus used to produce a liquid crystal substrate using squeegee coating technique. It consists of a biaxial mechatronic system which is synchronously controlled in vertical and horizontal directions scraping the liquid crystal substrates evenly on the surface of a petri dish. The thickness of the liquid crystal was profiled using laser diffraction technique and the homogeneity of the liquid crystal films produced was examined in a crossed-polarizing microscope. At an angular speed of 1500 rpm and under a shear stress of 1.46 ± 0.72 kPa, the squeegee coating was found producing liquid crystal films at a thickness of 132 ± 23 μm on the surface of petri dishes. With the application of this apparatus, evenly spread liquid crystal coatings with control thickness in petri dishes were consistently produced. This has overcome the major problem of manually coating the liquid crystal substrates using a cell scraper.

Nonlinear optical phenomena in fullerene-doped liquid crystal films and fibers

1995 ◽  
Author(s):  
Iam-Choon Khoo ◽  
Hong Li ◽  
Y. Liang ◽  
Ming Lee ◽  
B. Yarnell ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Nonlinear Optical ◽  
Liquid Crystal Films ◽  
Crystal Films ◽  
Optical Phenomena ◽  
Nonlinear Optical Phenomena

Polarization analysis of induced gratings in nematic liquid crystal films

1984 ◽  
Vol 62 (1) ◽  
pp. 40-44 ◽  
Author(s):  
Y. G. Fuh ◽  
R. F. Code
Keyword(s):  
Thin Films ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Detailed Analysis ◽  
Probe Laser ◽  
Polarization Analysis ◽  
Liquid Crystal Films ◽  
Crystal Films ◽  
Quantitative Separation ◽  
Simple Measurement

A detailed analysis of classical diffraction on the optically induced phase gratings in thin films of the nematic liquid crystals 5CB, 6CB, and MBBA is presented. It enables a quantitative separation of thermal contributions from reorientational contributions to the gratings to be made by a simple measurement of the gratings' diffraction efficiency with a polarized probe laser.

Surface Forces of the Electric Field Induced Flowin Nematic Liquid Crystals

1984 ◽  
Vol 39 (4) ◽  
pp. 309-319
Author(s):  
J. Grupp
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Elastic Constant ◽  
Surface Forces ◽  
Time Constants ◽  
Liquid Crystal Films ◽  
Viscosity Term ◽  
Crystal Films ◽  
Induced Flow

In thin nematic liquid crystal films with homeotropic boundaries, surface forces are measured that are produced by an electric field induced flow. The sample is placed between two horizontal circular glass disks in a torsion viscosimeter, where a torque is exerted on the upper disk by these surface forces. The evolution of the induced flow is registered via this torque. The time constants of this evolution, the viscosity term γ1 - α22/ηc and the elastic constant K3 are determined.

scholarly journals NONLINEAR OPTICAL STUDIES OF POLYMER INTERFACES

1994 ◽  
Vol 03 (04) ◽  
pp. 459-468 ◽  
Author(s):  
Y.R. SHEN
Keyword(s):  
Liquid Crystal ◽  
Nonlinear Optical ◽  
Polymer Surfaces ◽  
The Other ◽  
Polymer Interfaces ◽  
Optical Studies ◽  
Effective Surface ◽  
Liquid Crystal Films ◽  
Crystal Films ◽  
Metal Polymer

Second-order nonlinear optical processes can be used as effective surface probes. They can provide some unique opportunities for studies of polymer interfaces. Here we describe two examples to illustrate the potential of the techniques. One is on the formation of metal/polymer interfaces. The other is on the alignment of liquid crystal films by mechanically rubbed polymer surfaces.

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