Lasers with multiple feedbacks for wideband chaos generation

The unpredictable and random character of optical chaos can be used for secure communication, imaging
with chaotic lidar, or for random number generation. Generating wide-bandwidth optical chaos can be
achieved by coupling a semiconductor laser to optical feedback, i.e., a mirror at a distance. Using opti-
cal feedback is beneficial as it can be implemented on photonic integrated circuit platforms so that this
solution would be widely deployable. However, three main problems currently stand in the way of the
widespread use of these peculiar devices. First, the size of the system is too large. Second, the time-delay
signature (TDS), the distance between the laser and the mirror, manifesting itself in the output signal,
reduces the unpredictability. Third, the bandwidth of the optical chaos is limited and should be increased.
To address these problems, I propose to use multiple optical feedbacks. Specifically, I studied the laser
dynamics due to double optical feedback or feedback from a deformed microcavity, so-called asymmetric
resonant cavities (ARCs). To tackle the second problem, the TDS, we investigated new methods to
detect this signature based on all dynamical variables. We showed that using double optical feedback can
suppress the TDS without reducing the chaotic bandwidth. We demonstrated that the feedback phase is
a crucial parameter to control in this approach. Moreover, the feedback phase plays an important role in
the stability of this system. Finally, I studied ARCs to reduce the footprint further while suppressing the
TDS and increasing the chaotic bandwidth. We designed, manufactured, and experimentally tested these
devices and showed that they can be used to generate chaos in semiconductor lase.