Electrically switchable random to photonic band-edge laser emission in chiral nematic liquid crystals

Morris, Stephen M.; Gardiner, Damian J.; Hands, Philip J.W.; Qasim, Malik M.; Wilkinson, Timothy D.; White, I.H.; Coles, H. J.

doi:10.1063/1.3684804

Cited by 37 publications

(15 citation statements)

References 11 publications

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“…[14][15][16][17] In addition, DDLCs have been used to ll the inside of capillary bers or glass cells to reduce their lasing threshold because of the additional optical connement. [18][19][20] Recently, localized surface plasmon resonance (LSPR), a spectacular physical effect, have attracted a great deal of attention to provide strong electromagnetic eld connement or light trapping around the surface of nanostructures. When the incident photon energy matches the coherent electron oscillation frequency, 21 LSPR will be induced from collective electron oscillation on a surface of noble metallic nanoparticles, such as gold, silver and platinum.…”

Section: Introductionmentioning

confidence: 99%

Resonant energy transfer and light scattering enhancement of plasmonic random lasers embedded with silver nanoplates

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Resonant energy transfer and light scattering enhancement of plasmonic random lasers embedded with silver nanoplates

et al. 2020

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“…Apart from liquid crystal (LC) lasers based on the self-assembled helical structure, there are other DFB laser types grounded on artificially designed structures such as gratings [ 17 , 18 , 19 , 20 ]. On the other hand, CLCs have also been used in connection with other laser mechanisms such a leaky mode lasers [ 3 ] and random lasers [ 21 , 22 , 23 ], and references therein. However, in the present work we are going to focus ourselves exclusively on the so-called edge-mode and defect-mode CLC lasers.…”

Section: Introductionmentioning

confidence: 99%

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

2017

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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.

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“…A variation of the full-width at half maximum (FWHM) with applied frequency for Mix5 is shown in Figures 7 (a) and (b), where it can be seen that for low frequencies there is a characteristic sigmoid profile. For random lasers, the sharp decrease in FWHM corresponds to the excitation energy threshold [21], [22]. At high frequencies (e.g.…”

Section: Resultsmentioning

confidence: 99%

Improving the stability of organosiloxane smectic A liquid crystal random lasers using redox dopants

et al. 2015

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This report is focus on the development of liquid crystal (LC) visible-light scattering devices for random lasers. These light-scattering devices are based upon binary mixtures that consist of an organosiloxane smectic A LC and a wide temperature range nematogen LC. Both the temperature range of the smectic A phase and the dielectric anisotropy of the binary mixture are increased compared with that of the neat organosiloxane compound. In the latter case, the increase in the dielectric anisotropy results in a reduction of the magnitude of the electric field required to induce a clear state. Furthermore, it is found that the electric field threshold continues to decrease with increasing concentration of the nematic compound. For the random laser devices, the pyrromethene 597 laser dye was added to a mixture that was optimized for scattering and it was found that the absorption properties of the dye becomes unstable in the presence of the electro-hydrodynamic instabilities that are required to generate scattering in the LC cells. This is believed to be due to electro-chemical reactions that occur at the electrodes. To avoid dye degradation and ensure repeatable electro-optic behaviour, a reduction-oxidation (redox) couple is dispersed within the dye-doped binary mixture. It is shown that the addition of redox dopants helps to stabilize the dye in the scattering mixtures, and also increases the long-term repeatability of the scattering behaviour. Finally, we conclude by characterizing the random laser emission of the dye-doped binary mixture and demonstrate improved stability.

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Electrically switchable random to photonic band-edge laser emission in chiral nematic liquid crystals

Cited by 37 publications

References 11 publications

Resonant energy transfer and light scattering enhancement of plasmonic random lasers embedded with silver nanoplates

Resonant energy transfer and light scattering enhancement of plasmonic random lasers embedded with silver nanoplates

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

Improving the stability of organosiloxane smectic A liquid crystal random lasers using redox dopants

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