Four-wave interactions in an active XeCl plasma

A problem of the four-wave interaction of radiation in a three-level medium, where the lower working level is a repulsive one, is solved. This situation is characteristic of UV-active excimer molecules. The solution to this problem is compared to the results obtained for a two-level model. The coefficient of reflection into a conjugate wave is measured as a function of the small-signal gain in an active XeCl excimer plasma. An influence of the four-wave interaction on the characteristics of optical amplifiers and master oscillators operating with narrow-band radiation is observed.