Abstract

The use of coupled nonlinear cavities has allowed to generate extremely short pulses from many different lasers.^1–4 In such lasers, the signal circulating in the coupled cavity is self-phase-modulated due to the propagation in a material with a nonlinear index of refraction. Short pulse emission is favored when the coherent superposition of the signals circulating in the main (laser) cavity and in the coupled cavity produces a feedback that increases with intensity. Equivalently, the coupled cavity can be viewed as a nonlinear mirror whose reflectivity is controlled by the instantaneous value of the incident laser intensity. While the reflectivity of a two-wave interference coupled cavity (such as a nonlinear Michelson interferometer) varies sinusoidally with intensity, the reflectivity of a multiple-wave interference coupled cavity (of Fabry–Perot type) exhibits deterministic instabilities at large incident signals; as pointed out recently,⁵ the response of nonlinear Fabry–Perot cavities shows period-doubling and chaos. Such instabilities were experimentally observed⁶ when a Fabry–Perot cavity was illuminated with a continuous train of short pulses.

© 1994 IEEE