Random lasing from localized modes in strongly scattering systems consisting of macroporous titania monoliths infiltrated with dye solution

We have prepared random lasers that consist of macroporous titania monoliths infiltrated with dye solution and that operate close to light localization regime. When the excitation pulse energy exceeds a threshold, discrete spectral lines ascribed to laser oscillation appear on a featureless emission peak. No pulse-to-pulse variation was observed in the spectral positions of lasing lines, indicating that the lasing modes are localized in the medium. We demonstrated selective excitation of lasing modes by pumping at different positions on the sample. (C) 2010 American Institute of Physics. [doi:10.1063/1.3464962]