Laser action in temperature-controlled scattering media

We used a novel system based on a lower critical solution temperature (LCST) mixture containing a high gain laser dye to study laser actions in random scattering media. The LOST material comprised of hydroxypropyl cellulose (HPC) in water can be reversibly transformed from a transparent state to a highly scattering colloid as the temperature is increased above 41 degreesC. The resulting temperature-dependent scattering length and photon diffusivity in the presence of an amplifying optically pumped Kiton Red 620 laser dye can tune the linewidth of output spectrum from 30 to 5 nm. Besides its suitability for random laser studies, this system may find its applications in remote temperature sensing and displays. (C) 2002 Elsevier Science B.V. All rights reserved.