The influence of structure and environment on spectroscopic and lasing properties of dye-doped glasses

A new class of hemicyanine dyes was studied as laser dyes. From the influence of structure and solvent effects on the spectroscopic and lasing properties, a basic understanding of the involved processes was obtained. The studied dyes were found to have two distinguishable mesomeric forms, one predominant in the ground-state, and the other in the excited state, leading to a large Stokes shift. The dyes exhibited low fluorescence quantum yields, which were attributed to the presence of a counter iodide ion, which increases singlet-to-triplet intersystem crossing, and to a twisted intramolecular charge-transfer (TICT) of the amino moiety. However, significant lasing efficiencies were observed under pulsed pump conditions, possibly because the stimulated emission competes with the nonradiative processes. The laser losses are mainly due to the cavity. Solvent effect studies showed that the chromophore is very sensitive to hydrogen bonding donor (HBD) solvents. The dye-doped sol-gel composite glass exhibits a behavior close to that of water, suggesting that the dye is attached to the silica skeleton of the composite glass through a hydrogen bonding. Energy transfer between two dyes codoping a multiphasic composite glass was found to be insignificant; therefore, this composite exhibited simultaneous lasing from both dyes. Codoped tunablity was achieved through the range of both dyes, from 560 to 610, nm with an average efficiency of 7%. The lasing properties of this lasing medium was studied and compared to reference dye solutions.