Event detection methods distinguish different emission regimes in a semiconductor laser with optical feedback

In semiconductor lasers, optical feedback generates different types of oscillations. Depending on the laser and feedback parameters, the emission regimes can be classified in three main types: stable emission, Low Frequency Fluctuations (LFFs) and Coherence Collapse (CC). In the stable regime, the intensity signal shows noisy fluctuations, while in the LFF regime, these fluctuations are suddenly interrupted by large drops, during which the laser almost turns off. These reset-type events are separated by time intervals of stable emission, where the intensity displays only small fluctuations. In the CC regime, the intensity signal shows highly irregular fluctuations. We analyze experimental intensity time traces, and, by combining three event-detection methods that detect different numbers of events, and using a clustering algorithm, we show that time traces can be qualitatively distinguished within these regimes. We also find that the event-detection methods capture the gradual or abrupt nature of the transitions between the different regimes.