Molecular engineering and photostability of laser dyes within sol-gel hosts

The use of a solid-state dye laser for commercial applications has been limited largely by the poor photostability of the gain medium. Techniques are examined to improve the photostability of Coumarin and Pyrromethene-BF₂ 567 (PM-567) laser dyes within xerogel and Polyceram hosts synthesized by sol-gel processing. The photochemical mechanisms by which laser dyes degrade are discussed and determined specifically for PM-567. PM-567 was determined to degrade both by photo-oxidation and acid degradation. Techniques for improving photostability are described from a molecular engineering perspective. These techniques include: covalently attaching the laser dye to the host; controlling the chemical environment of the dye; increasing dye caging by increasing the SiO₂ content; removing porosity from the host; and incorporating additives such as hindered amine light stabilizers to minimize photodegradation.