Anomalous frequency pulling in the photorefractive oscillators

Ramon Herrero, Daniel Hennequin

Phys. Rev. A 60 1679 (1999)

The emission frequency of an optical oscillator is not, in general, the cavity frequency, because it results from a compromise between the cavity and the material (atom, crystal) frequencies: this phenomenon is known as frequency pulling. We study in this paper the mechanisms leading to frequency pulling in oscillators with photorefractive gain (OPG), and compare them with those of lasers. We find that because the pulling in OPG does not depend explicitly on the empty cavity mode frequency, behaviors different from those observed in lasers are obtained. In particular, for a given set of parameters, the frequency pulling has a constant sign, so that the emission frequency is always larger (or smaller) than the maximum gain frequency. This leads to the counterintuitive effect that, in some conditions, the emitted intensity could decrease as the losses are decreased.