Thermo-recurrent nematic random laser

This experimental work is aimed to investigate the thermal
behavior of random laser action in dye doped nematic liquid crystals. The
study evidenced an important temperature dependence of the random lasing
characteristics in the nematic phase and in close proximity of the nematicisotropic
(N-I) phase transition. A lowering of the laser emission intensity as
the temperature increases is strictly related to the shift of the lasing
threshold as function of the temperature even though the pump energy is
kept fixed. The optical losses increasing owing to the thermal fluctuation
enhanced scattering drive the input-output smoother behavior until the
system stops to lase, because below threshold. The unexpected reoccurrence
of random lasing at higher temperature, in proximity of N-I transition is
found to be related to a different scattering mechanism, the micro-droplets
nucleation and critical opalescence.