Superradiant emission at 5106, 5700, and 5782 Å in pulsed copper iodide discharges

Superradiant laser emission at 5106, 5700, and 5782 A is reported from pulsed discharges in copper iodide vapor at temperatures near 600°C. This conclusion is supported by pulse shortening of the visible emission and a marked increase in the relative visible intensity compared to the copper resonance radiation as the critical temperature range is approached. Electrical dissociation of the copper iodide, electron impact excitation of the copper atoms, and radiation trapping of the 3248- and 3274-A resonance lines are proposed as the principal inversion mechanisms. Below \sim450\deg C, where insufficient copper iodide is vaporized to provide resonance trapping, the upper laser level lifetimes are ∼10 ns, whereas at higher temperatures trapping is complete and the effective 2 P 3/2 and 2 P 1/2 lifetimes are 615 and 370 ns, respectively. The reservoir temperature at which stimulated emission is observed is in good agreement with calculations of the threshold ground-state copper densities required for resonance trapping. These experiments indicate that practical copper laser systems operating at substantially reduced temperatures can be developed provided instabilities in the copper iodide discharges can be overcome.