The optical whistle: a novel transverse oscillation in nonlinear optical cavities

In the 1980´s a great deal of work concentrated on the transverse structure and dynamics in nonlinear cavities, in order to incorporate the phenomena of self-(de)focusing and diffraction. In particular, McLaughlin et al. demonstrated in 1985 that a finite-width Gaussian input beam incident on a cavity with a single transverse dimension gives rise to a transverse instability in the cavity field; this process is a form of modulational instability. However, their linearized analysis leaves an important question unanswered: what happens when these perturbations grow large? What type of asymptotic state does the field profile approach? We have found that a number of solutions are possible: the system can approach a steady state, it can exhibit intermittency and chaos, or it can undergo periodic oscillations. We term a cavity driven into the latter solution an optical whistle. Within this periodic mode the oscillation frequency is roughly proportional to the input field amplitude; hence the nonlinear cavity acts as a light-controlled oscillator. Experiments are underway to observe this effect