Effects of optical feedback on femtosecond supercontinuum generation

A femtosecond supercontinuum generating system is presented by employing a microstructured fiber within a synchronously pumped ring resonator. Via the ring resonator, optical feedback is introduced, which leads to the creation of a highly nonlinear oscillator and to the formation of nonlinear dynamics like period multiplication, limit cycle, and chaos. The effect of delayed feedback on supercontinuum generation is studied numerically and experimentally, using the input pulse power and the resonator length detuning as control parameters. In combination, these two control parameters allow for a systematical adjustment of the regimes of nonlinear dynamics, which leads to an alteration of the pattern of pulse trains. Changing the resonator length on a sub-wavelength scale enables manipulation of the feedback phase, which can be used to adjust shape and bandwidth of the optical spectrum. Furthermore, a possibility to tailor the modes of the optical frequency comb is demonstrated, and the influence of the feedback phase on the noise properties of the supercontinuum generating system is discussed.

► We investigate femtosecond supercontinuum with optical feedback.
► Supercontinuum with feedback displays period multiplication, limit cycle and chaos.
► Adjusting the feedback phase enables fine-tuning of the optical spectrum.
► Amplitude noise reduction by the optical feedback loop by 15 dB is demonstrated.