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Materials 2018, 11(1), 5; https://doi.org/10.3390/ma11010005

Upgrading the Performance of Cholesteric Liquid Crystal Lasers: Improvement Margins and Limitations

1
Department of Applied Physics II, Faculty of Science and Technology, University of the Basque Country, UPV/EHU, 48080 Bilbao, Spain
2
Department of Condensed Matter Physics, Faculty of Science and Technology, University of the Basque Country, UPV/EHU, 48080 Bilbao, Spain
*
Author to whom correspondence should be addressed.
Received: 6 November 2017 / Revised: 5 December 2017 / Accepted: 19 December 2017 / Published: 21 December 2017
(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)
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Abstract

The topic of cholesteric-liquid-crystal lasers is a rapidly expanding research area in the field of soft-matter photonics. The increasing interest in this field is due to the high versatility that these lasers may possibly present and the prospects of giving rise to new miniaturized devices. However, further improvements in their operation capabilities are still required for potential applications. In this paper, we critically analyze the main strategies proposed up to now to optimize their performance. We show theoretically and experimentally that possible innovations in the device structure cannot produce lasers with threshold energies below a certain limit. This limit is determined by the light scattering and absorption losses inside the liquid crystal. Even assuming the case of samples free of defects and perfectly non-absorbing, an intrinsic light scattering, typical of mesogens, still remains. Numerical estimates of the thresholds indicate that these lasers could hardly be driven by compact light sources such as current electroluminescent or light-emitting diodes. Since the improvement possibilities regarding cell architecture seem to be exhausted, the advance must come from the use of new dye molecules. These molecules should show enhanced emission cross-sections and be efficiently integrable within the mesogenic solvent. In addition, the fluorescent systems must present very small quantum yields to triplet states if continuous-wave lasing is sought. In this respect, quantum dots are an alternative to explore for further investigations. View Full-Text
Keywords: cholesteric liquid crystals; lasers; photonic materials cholesteric liquid crystals; lasers; photonic materials
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Ortega, J.; Folcia, C.L.; Etxebarria, J. Upgrading the Performance of Cholesteric Liquid Crystal Lasers: Improvement Margins and Limitations. Materials 2018, 11, 5.

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