Reversible phototuning of lasing frequency in dye doped cholesteric liquid crystal and ways to improve it [Invited]

A new method of lasing frequency phototuning was studied for dye-doped cholesteric liquid crystal (CLC) mixtures of azoxy-nematic ZhK-440 and cholesterol derivatives by variation of their helical pitch under irradiation by light of different wavelengths. For most lasing dyes introduced into CLC systems the fluorescence quantum yield becomes substantially lower at weight concentrations 0.3-0.5%, which hinders realization of lasing. A dye of pyrromethene class has been found, showing fluorescence quantum yield of more than 50% at the above-indicated concentrations. Lasing of distributed feedback (DFB) laser in CLC on the basis of azoxy nematic ZhK-440 has been obtained, and conditions were studied for minimization of its threshold and broadening of the reversible phototuning frequency range (C) 2011 Optical Society of America