On the finesse of a phase-conjugate Fabry-Perot resonator using nearly-degenerate four-wave mixing

We consider a Fabry-Perot cavity in which one of the mirrors is a phase-conjugate mirror (PCM) using near-degenerate four-wave mixing. We show that when taking pump depletion into account, the divergence in finesse of the resonator predicted by linear theories for a resonator round trip gain approaching unity is eliminated. The saturation of the finesse as a function of pump intensity leads to a new kind of bistability in the transmission characteristics of the system.