Photochemical studies on organic lasers

The fluorescence emission from alcoholic solutions of 7-monoalkyl-amino-4-methyl coumarins shifts from blue to blue-green on the addition of acid. Fluorescence and excitation spectra measured, and lasing species are discussed. New laser dyes based on the coumarin skeleton have been synthesized by varying the substituent groups at the 3- and 7-positions. 7-Amino-coumarins which were partially or totally alkylated were efficient lasers. The presence of a benzthiazole group at the 3- position shifted the laser emission to the green region. New laser dyes of the pyridine class were also synthesized. These were effective in the violet region of the spectrum.