OPTICAL SOURCES HAVING A STRONGLY SCATTERING GAIN MEDIUM PROVIDING LASER-LIKE ACTION

摘要

A gain medium is comprised of a multi-phase system wherein: a first phase isan electromagnetic radiation emission phase; a second phase is anelectromagnetic radiation scattering phase; and a third phase is a transparentmatrix phase. By example, the emission phase may consist of dye molecules, thescattering phase may consist of high contrast particles, and the matrix phasemay consist of a solvent such as methanol. In some embodiments of thisinvention the emission and scattering phases may be the same phase, as whensemiconductor particles are employed. A smallest dimension of a body comprisedof the gain medium may be less than a scattering length associated with thescattering phase. It is shown that nearly thresholdless laser behavior isobserved in strongly scattering optically pumped dye-methanol solutionscontaining colloidal TiO2 or Al2O3 ruby nanoparticles. The emission from thehigh gain colloid exhibits a slope change in the linear input-outputcharacteristics above a critical pump pulse energy. The change in slope isaccompanied by a spectral line narrowing with a bichromatic spectrum appearingat high pump energies.