Simulation of light generation in cholesteric liquid crystals using kinetic equations: Time-independent solution

Shtykov, N. M.; Palto, S. P.; Umanskiĭ, B. A.

doi:10.1134/s1063776113080190

Cited by 4 publications

(5 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Evidently that equation does not hold in the limit of CW regime, but fortunately that case has been explicitly worked out in ref. [ 57 ] for a two-level system. The resulting threshold intensity I th is

…”

Section: Methodsmentioning

confidence: 99%

“…

/N (%) is the percentage of the dye population in the excited state required for laser emission relative to the total number of dye molecules. In the case of simple cells approximate analytical expressions for

have been given in the literature [ 56 , 57 ]:

…”

Section: Theoretical Analysis Of Different Cell Architecturesmentioning

confidence: 99%

“…In principle,

is related to the dwelling time τ c of laser photons in the cavity in the absence of losses by means of the expression [ 57 ]:

where n is an average refractive index and c the speed of light in vacuum. These are the

values shown in Table 2 .…”

Section: Theoretical Analysis Of Different Cell Architecturesmentioning

confidence: 99%

See 2 more Smart Citations

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

2017

View full text Add to dashboard Cite

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.

show abstract

…”

Section: Methodsmentioning

confidence: 99%

“…

have been given in the literature [ 56 , 57 ]:

…”

Section: Theoretical Analysis Of Different Cell Architecturesmentioning

confidence: 99%

See 1 more Smart Citation

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

2017

View full text Add to dashboard Cite

show abstract

“…γ ∥ th is related with other parameters easier to interpret and more used in practice, such as the photon dwelling time in the cavity τ c = λ/(2πcγ ∥ th ) or the threshold for the population inversion of dyes 16,46…”

Section: ■ Experimental Resultsmentioning

confidence: 99%

“…Usually, the lower the γ ∥ th parameter the better the laser performance. In the case of normal incidence, approximate analytical expressions for γ ∥ th have been given in the literature where L is the sample thickness and α is a parameter related to the anisotropy of the refractive indices, γ ∥ th is related with other parameters easier to interpret and more used in practice, such as the photon dwelling time in the cavity τ c = λ/(2 πcγ ∥ th ) or the threshold for the population inversion of dyes , where σ e is the cross section of fluorescent emission for the corresponding polarization eigenstate at the laser wavelength and c is the speed of light in vacuum. Essentially n 2 th is a direct measure of the laser threshold energy.…”

Section: Discussionmentioning

confidence: 99%

Cone-Shaped Emissions in Cholesteric Liquid Crystal Lasers: The Role of Anomalous Scattering in Photonic Structures

2018

View full text Add to dashboard Cite

The out-of-normal emission in cholesteric liquid-crystal lasers is studied experimental and theoretically. Apart from the well-known dominant laser in the direction of the helix axis, three other types of radiation, with cone-shaped spatial patterns, are identified and characterized. The physical mechanisms responsible for the different emissions are clarified. One of the radiations is a weak colorful lasing emission whose wavelength changes continuously depending on the propagation direction. The wavelengths of the other two radiations take place at the longwavelength and short-wavelength edges of the photonic bandgap. These emissions are attributed to an anomalous scattering phenomenon that gives rise to energy transfer from the main laser beam to some specific directions where the amount of final photonic states is high. An expression for the scattering cross section, reminiscent of Fermi's golden rule for spontaneous emission in photonic structures, is proposed. Some other phenomena independent of the lasing occurrence but driven by the anomalous scattering are briefly presented.

show abstract

Role of the sample thickness on the performance of cholesteric liquid crystal lasers: Experimental, numerical, and analytical results

Sanz-Enguita

Ortega

Folcia

et al. 2016

Journal of Applied Physics

View full text Add to dashboard Cite

We have studied the performance characteristics of a dye-doped cholesteric liquid crystal (CLC) laser as a function of the sample thickness. The study has been carried out both from the experimental and theoretical points of view. The theoretical model is based on the kinetic equations for the population of the excited states of the dye and for the power of light generated within the laser cavity. From the equations, the threshold pump radiation energy Eth and the slope efficiency η are numerically calculated. Eth is rather insensitive to thickness changes, except for small thicknesses. In comparison, η shows a much more pronounced variation, exhibiting a maximum that determines the sample thickness for optimum laser performance. The predictions are in good accordance with the experimental results. Approximate analytical expressions for Eth and η as a function of the physical characteristics of the CLC laser are also proposed. These expressions present an excellent agreement with the numerical calculations. Finally, we comment on the general features of CLC layer and dye that lead to the best laser performance.

show abstract

Simulation of light generation in cholesteric liquid crystals using kinetic equations: Time-independent solution

Cited by 4 publications

References 13 publications

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

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

Cone-Shaped Emissions in Cholesteric Liquid Crystal Lasers: The Role of Anomalous Scattering in Photonic Structures

Role of the sample thickness on the performance of cholesteric liquid crystal lasers: Experimental, numerical, and analytical results

Contact Info

Product

Resources

About