The transition of the single-frequency oscillation of a semilinear photorefractive coherent oscillator for sufficiently large coupling strengths into two-frequency oscillation is predicted and is observed experimentally. The critical value of coupling strength at which the bifurcation occurs is a function of pump-intensity ratio and cavity losses. For certain combinations of these parameters, the critical coupling strength for spectrum bifurcation becomes smaller than the threshold coupling strength: in these cases double-frequency oscillation appears at the threshold. The supercritical bifurcation in the oscillation spectrum is analogous to the second-order phase transition.
© 2002 Optical Society of America
(190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
(190.5040) Nonlinear optics : Phase conjugation
(190.5330) Nonlinear optics : Photorefractive optics
(230.4910) Optical devices : Oscillators
Pierre Mathey, Serguey G. Odoulov, and Daniel Rytz, "Oscillation spectra of semilinear photorefractive coherent oscillator with two pump waves," J. Opt. Soc. Am. B 19, 2967-2977 (2002)