First order optical phase transitions in photorefractive coherent oscillators

Summary form only given. Recently the analogy with phase transition was revealed for photorefractive coherent oscillators. It has been shown that the onset of oscillation in the ring-loop oscillator and double phase conjugate mirror exhibits similar features as second order phase transition: (1) the numerous small-amplitude photorefractive gratings responsible for light-induced scattering below the transition point evolve into one high-amplitude grating which couples the pump and oscillation waves; (2) the oscillation wave intensity is increasing gradually with coupling strength /spl gamma/I from zero at the threshold; and (3) the critical slowing down is observed in temporal development of the light-induced scattering. The purpose of this report is to show that some other photorefractive oscillators exhibit the threshold behaviour similar to the first order phase transition.