Evolution from low-frequency fluctuations to high-dimension chaos in semiconductor laser with optical feedback

Extensive experiment studies are performed in the evolved process from low-frequency fluctuations to chaos. The low-frequency fluctuations and high dimension chaos with 12.2 correlation dimension are generated experimentally by a DFB semiconductor laser with optical feedback. Meanwhile, the effects of pumping cur-rent and feedback strength on the average duration and the peak-peak value of low-frequency fluctuations are experimentally analyzed. Our results show that there exists an obvious critical point for the bias current of the semiconductor laser. When the bias cur-rent I-b is set below 1.03I(th), the peak-peak value of the low-frequency fluctuations is increasing at first and then decreasing with the feedback strength decreasing, while its average duration is decreasing but chaos don't appear in the whole performance. However, when the bias current I-b is set above 1.03I(th), the output of the laser can evolutes from low-frequency fluctuations chaos with the feedback strength decrease. Moreover the peak-peak value of the low-frequency fluctuation is increasing continually and its average periodic time is decreasing with the decrease of the feedback strength.