Time dependence of the gain of an optically pumped solution of rhodamine 6G

The time dependence of the gain of an ethanol solution of rhodamine 6G was determined during excitation with conventional lamps producing pulses of 80 μsec duration. The gain maximum was reached much earlier than the maximum of the excitation pulse. It was demonstrated experimentally that because of insufficient chemical purity of the solution, the gain was replaced by a reversible absorption due to an increase in the singlet-triplet conversion probability.