OSCILLATORY-TO-NON-OSCILLATORY TRANSITION DUE TO EXTERNAL NOISE IN A PARAMETRIC OSCILLATOR

A degenerate parametric oscillator which is driven by a random current additionally applied to a sinusoidal pumping current is found to exhibit a new type of oscillatory-to-nonoscillatory transition. This noise-induced phase transition has a different kind of critical behavior from that observed in usual phase transitions, that is, near the threshold the variance of the fluctuating output current remains constant, however, the critical slowing-down does occur. A stochastic equation for the parametric oscillation which includes a random force multiplied by the amplitude itself is derived and the experimental results are fully accounted for in terms of that equation.