Intensity extrema in optically injected Fabr - Perot cavities with saturable gain

An optically injected Fabry- Perot cavity containing uniform saturable gain is analyzed. Familiar cubic curves of laser intensity vs injected intensity are obtained for single-ended lasers. The curves for the intensity returning to the injected end of double- ended lasers can have loops, cusps, and undulations if the mirror reflectivities and small- signal gain are properly chosen. The undulations can also occur in doubleended regenerative amplifiers.