Singly resonant optical parametric oscillator with external signal injection

An approximate theory is used in a study of the characteristics of a singly resonant optical parametric oscillator (SROPO) in the case when an external signal is injected at the frequency of the resonant signal wave. It is shown that such injection can alter significantly the nature of the radiation emitted by an SROPO. In particular, when the intensities of the injected signal and of the pump radiation are sufficiently high, the intensity of the signal wave may exhibit a bistable dependence on the pump and injected signal intensities.