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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:35 |
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Conference: Bucharest University Faculty of Physics 2023 Meeting
Section: Polymer Physics
Title:
Particular Characteristics of Controllable Dye-Doped Nematic Liquid Crystal Optical Micro-Emitters
Authors:
Valentin BARNA(1)
Affiliation:
1) University of Bucharest, Faculty of Physics, PO Box MG 11, Magurele-Bucharest, Romania
E-mail
valentin.barna@g.unibuc.ro
Keywords:
Optical Micro Lasers, Liquid Crystals, Phase Trasition
Abstract:
Random laser effect in a confined, partially ordered, dye doped nematic liquid crystals with long-range dielectric tensor fluctuations are presented. Coherent backscattering of light waves in orientationally ordered nematic liquid crystals shows a weak localization of light which strongly supports diffusive laser action, when in presence of a gain medium (dye molecules). Beyond a certain optical pumping energy value, sequences of brilliant small lights appear on the background screen, emerging from our sample. A strongly fluctuating spatio-temporal random laser emission pattern (spectral width ca. 0.5 nm FWHM) is then measured. Experimental data disclose a high temperature dependency of the lasing properties in the nematic phase and in close vicinity of the nematic-isotropic (N-I) phase transition. The surprising reoccurrence of random lasing at higher temperatures, near the N-I transition is explained to be related to a different scattering mechanism, due to the micro-droplet phase nucleation.
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