Laser-pumped Stimulated Emission from Organic Dyes: Experimental Studies and Analytical Comparisons

Stimulated emission spectra of two organic dyes, chloro-aluminum phthalocyanine (CAP) and 3,3′-diethylthiatricarbocyanine iodide (DTTC) are compared. Giant-pulse ruby laser excitation was used in both cases. An end pumping configuration employed with DTTC resulted in narrow beam divergences and high conversion efficiencies. For CAP, the oscillating transition is one which terminates on an excited vibrational level of the ground electronic state. For DTTC, stimulated emission at the lowest concentrations occurs at the peak of the Franck–Condon-shifted fluorescence band but moves to longer wavelengths as the concentration is increased. The transient behavior of the CAP laser, pumped in a transverse geometry, was observed and compared with computer solutions of the rate equations. Polarization measurements of the laser beams were also made. An analysis is given of requirements for achieving optimal pumping by means of flashlamps.
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[The paper concludes with an addendum reporting recent observations of stimulated emission from dye solutions lasing at wavelengths ranging from blue (4385 Å) to orange (6000 Å)].