Photonics and lasing in liquid crystal materials

2006 ◽  
Vol 364 (1847) ◽  
pp. 2747-2761 ◽  
Author(s):  
Peter Palffy-Muhoray ◽  
Wenyi Cao ◽  
Michele Moreira ◽  
Bahman Taheri ◽  
Antonio Munoz
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Photonic Band Gap ◽  
Stop Band ◽  
Soft Materials ◽  
Modulated Phases ◽  
Photonic Band Gap Materials ◽  
Liquid Crystal Elastomers ◽  
Photon States ◽  
Liquid Crystal Materials

Owing to fundamental reasons of symmetry, liquid crystals are soft materials. This softness allows long length-scales, large susceptibilities and the existence of modulated phases, which respond readily to external fields. Liquid crystals with such phases are tunable, self-assembled, photonic band gap materials; they offer exciting opportunities both in basic science and in technology. Since the density of photon states is suppressed in the stop band and is enhanced at the band edges, these materials may be used as switchable filters or as mirrorless lasers. Disordered periodic liquid crystal structures can show random lasing. We highlight recent advances in this rapidly growing area, and discuss future prospects in emerging liquid crystal materials. Liquid crystal elastomers and orientationally ordered nanoparticle assemblies are of particular interest.

3-Dimensional Photonic Crystals at Optical Wavelengths

1998 ◽  
Vol 07 (02) ◽  
pp. 181-200 ◽  
Author(s):  
S. G. Romanov
Keyword(s):  
Photonic Crystals ◽  
Band Gap ◽  
Photonic Band Gap ◽  
Stop Band ◽  
High Refractive Index ◽  
3 Dimensional ◽  
Optical Wavelength ◽  
Photonic Band Gap Materials ◽  
Optical Wavelengths ◽  
Photonic Band

Different experimental strategies towards the 3-dimensional photonic crystals operating at optical wavelength are classified. The detailed discussion is devoted to the recent progress in photonic crystals fabricated by template method — the photonic band gap materials on the base of opal. The control of photonic properties of opal-based gratings is achieved through impregnating the opal with high refractive index semiconductors and dielectrics. Experimental study demonstrated the dependence of the stop band behaviour upon the type of impregnation (complete or partial) and showed a way for approaching complete photonic band gap. The photoluminescence from opal- semiconductor gratings revealed suppression of spontaneous emission in the gap region with following enhancement of the emission efficiency at the low-energy edge of the gap.

Swelling dynamics of liquid crystal elastomers swollen with low molecular weight liquid crystals

2004 ◽  
Vol 69 (2) ◽  
Author(s):  
Yusril Yusuf ◽  
Yukitada Ono ◽  
Yusuke Sumisaki ◽  
P. E. Cladis ◽  
Helmut R. Brand ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Low Molecular Weight ◽  
Liquid Crystal Elastomers

Thermoresponsive Inverse Opal Films Fabricated with Liquid-Crystal Elastomers and Nematic Liquid Crystals†

Langmuir ◽  
2011 ◽  
Vol 27 (4) ◽  
pp. 1505-1509 ◽  
Author(s):  
Guanglong Wu ◽  
Yin Jiang ◽  
Dan Xu ◽  
Hong Tang ◽  
Xiao Liang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Inverse Opal ◽  
Liquid Crystal Elastomers

LASER ACTION IN DYE DOPED LIQUID CRYSTALS: FROM PERIODIC STRUCTURES TO RANDOM MEDIA

2009 ◽  
Vol 18 (03) ◽  
pp. 349-365 ◽  
Author(s):  
A. DE LUCA ◽  
V. BARNA ◽  
S. FERJANI ◽  
R. CAPUTO ◽  
C. VERSACE ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Disordered Systems ◽  
Random Media ◽  
Light Transmission ◽  
Periodic Structures ◽  
Photonic Band Gap ◽  
Stop Band ◽  
Laser Action ◽  
Spectral Position ◽  
Laser Array

The birefringence and natural ability to form periodic structures make cholesteric liquid crystalline (CLC — chiral nematics) materials particularly attractive as 1D photonic band gap systems. If a CLC is doped with dye fluorescent molecules, in such a way that the maximum peak of fluorescence matches one of the edges of the selective stop band, laser action is expected at that spectral position. By confining the helical super-structure of chiral liquid crystals in polymeric micro-cavity channels, a tunable microcavity laser array was achieved. In multiple scattering systems, the propagation of the light waves is quite different, as optical scattering may induce a phase transition in the photon transport behavior. Beyond a critical scattering level, the system makes a transition into a strongly localized state and light transmission is inhibited. This effect can be used as a photon trapping mechanism to obtain laser action in the presence of a gain medium. Random lasing modes come from interference effects which survive in disordered systems and open a particular chapter in the study of the interplay between localization and amplification. Here, experiments performed on systems having different order degree and confinement are presented and possible technological implications are discussed.

scholarly journals Evaluating the Concentration of Ions in Liquid Crystal Cells: Hidden Factors and Useful Techniques

Proceedings ◽  
2021 ◽  
Vol 62 (1) ◽  
pp. 10
Author(s):  
Yuriy Garbovskiy
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Fields ◽  
Measurement Techniques ◽  
Ion Concentration ◽  
Ion Generation ◽  
Concentration Of Ions ◽  
Generation Mechanisms ◽  
Crystal Cells ◽  
Liquid Crystal Materials

Many liquid crystal devices are driven by electric fields. Ions, typically present in molecular liquid crystal materials in minute quantities, can compromise the performance of mesogenic materials (in the simplest case, through a well-known screening effect). Even highly purified liquid crystals can be contaminated with ions during their production and handling. Therefore, measurements of the concentration of ions have become an important part of the material characterization of liquid crystals. Interestingly, even a brief analysis of existing publications can reveal a quite broad variability of the values of the concentration of ions measured by different research groups for the same liquid crystals. This reflects the complexity of ion generation mechanisms in liquid crystal materials and their dependence on numerous factors. In this paper, an overview of ion generation mechanisms in liquid crystals and modern ion measurement techniques is followed by the discussion of frequently overlooked factors affecting the measured values of the ion concentration. Ion-generating and ion-capturing properties of the alignment layers (or substrates) of liquid crystal cells are considered and used to evaluate a true concentration of ions in liquid crystals. In addition, practical recommendations aimed at improving the measurements of the ion density in liquid crystals are also discussed.

Luminescent liquid crystals bearing an aggregation-induced emission active tetraphenylthiophene fluorophore

2019 ◽  
Vol 7 (16) ◽  
pp. 4828-4837 ◽  
Author(s):  
Ling-Xiang Guo ◽  
Yi-Bo Xing ◽  
Meng Wang ◽  
Ying Sun ◽  
Xue-Qin Zhang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Aggregation Induced Emission ◽  
Liquid Crystal Materials

In this work, six novel luminescent liquid crystal materials bearing an aggregation-induced emission active tetraphenylthiophene fluorophore are described.

scholarly journals Liquid Crystal Elastomers for Biological Applications

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 813
Author(s):  
Mariam Hussain ◽  
Ethan I. L. Jull ◽  
Richard J. Mandle ◽  
Thomas Raistrick ◽  
Peter J. Hine ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Stimuli Responsive ◽  
Absorption Properties ◽  
Liquid Crystal Elastomer ◽  
Cell Scaffolds ◽  
Artificial Tissue ◽  
Recent Developments ◽  
Liquid Crystal Elastomers ◽  
Potential Use

The term liquid crystal elastomer (LCE) describes a class of materials that combine the elastic entropy behaviour associated with conventional elastomers with the stimuli responsive properties of anisotropic liquid crystals. LCEs consequently exhibit attributes of both elastomers and liquid crystals, but additionally have unique properties not found in either. Recent developments in LCE synthesis, as well as the understanding of the behaviour of liquid crystal elastomers—namely their mechanical, optical and responsive properties—is of significant relevance to biology and biomedicine. LCEs are abundant in nature, highlighting the potential use of LCEs in biomimetics. Their exceptional tensile properties and biocompatibility have led to research exploring their applications in artificial tissue, biological sensors and cell scaffolds by exploiting their actuation and shock absorption properties. There has also been significant recent interest in using LCEs as a model for morphogenesis. This review provides an overview of some aspects of LCEs which are of relevance in different branches of biology and biomedicine, as well as discussing how recent LCE advances could impact future applications.

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