Coherent approaches on chaotic semiconductor lasers for dimensional enhancement

Chaotic dynamics in semiconductor lasers under feedback is useful for ranging, security, reinforcement learning, and random bit generation. Complementing temporal characterizations, geometric characterization is realized using the correlation dimension D2. Numerically, a coherent combination of injection and feedback on a laser is considered in showing dimensional enhancement that qualitatively agrees with recent experiments. Experimentally, measurements of the dimensions continue to show enhancement in complexity by coherently incorporating injection and feedback without fixing the phase. The measurements are enabled by employing a large data size, while re-embedding through including a principal component analysis (PCA) is considered. Also, balanced homodyning with a delay is considered on a laser under injection alone, where the estimated dimension is found to nearly double as the baseband is strengthened. Based on single-mode laser dynamics, the coherent approaches of continuous-wave injection, delayed feedback, and balanced homodyning are demonstrated for manipulating the chaotic complexity for applications.