UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2022-07-01 17:42

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Conference: Bucharest University Faculty of Physics 2019 Meeting


Section: Polymer Physics


Title:
Liquid Crystals Dye-Doped MicroLasers


Authors:
Valentin BARNA(1)


Affiliation:
1) University of Bucharest, Faculty of Physics, PO Box MG 11, Magurele-Bucharest, Romania


E-mail
barnavalentin@yahoo.com


Keywords:
mirror-less lasers, random lasing, dye-doped liquid crystals, emission efficiency


Abstract:
Lasing phenomena in disordered media, referred to as "random lasing" have been the subject of intense theoretical and experimental studies. These systems are captivating examples of scientific topics that synergize multiple scattering of light and optical amplification. In a random laser several discrete modes are optically amplified within the host medium and exhibit individual resonant wavelengths with the spectral interval being usually in the range of a few nanometers. Laser action is validated for wedge cell geometries, freely suspended thin gel films and irregularly shaped droplets of various viscosities in systems fabricated from dye-doped liquid crystals. Nanosecond and femtosecond pumping conditions are investigated and compared. Optical emission characteristics such as low emission band FWHM (0.5 nm), lasing energy threshold, emission efficiency, far field spatial emission profiling, confirm the occurrence of light amplification and that, specifically, laser emission is generated in our cavity-less devices. Unlike distributed feedback mirror-less lasers, these systems can be considered as cavity-less amplifiers where the disorder unexpectedly plays the most important role, behaving as randomly distributed feedback lasers.