Steady states of a χ³ parametric oscillator with coupled polarizations

Polarization effects in the microcavity parametric oscillator are studied using a simple model in which two χ³ optical parametric oscillators are coupled together. It is found that there are, in general, a number of steady states of the model under continuous pumping. There are both continuous and discontinuous thresholds, at which new steady states appear as the driving intensity is increased: at the continuous thresholds, the new state has zero output intensity, whereas at the discontinuous threshold it has a finite output intensity. The discontinuous thresholds have no analog in the uncoupled device. The coupling also generates rotations of the linear polarization of the output compared with the pump, and shifts in the output frequencies as the driving polarization or intensity is varied. For large ratios of the interaction between polarizations to the interaction within polarizations, of the order of 5, one of the thresholds has its lowest value when the pump is elliptically polarized. This is consistent with recent experiments in which the maximum output was achieved with an elliptically polarized pump.