Systems with delayed interactions play a prominent role in a variety of fields, ranging from traffic and population dynamics, gene regulatory and neural networks or encrypted communications.
When subjecting a semiconductor laser to reflections of its own emission, a delay results from the propagation time of the light in the external cavity. Because of its experimental accessibility and multiple applications, semiconductor lasers with delayed feedback or coupling have become one of the most studied delay systems.
The feedback delay in the external laser cavity is typically large compared to the timescale on which a semiconductor laser operates, and can induce chaotic dynamics. When coupling multiple semiconductor lasers, the delay in the coupling gives rise typical patterns of chaos synchronisation, which can be used in applications as encrypted communication or information processing.
Dr D’Huys compares the dynamics of a single laser with feedback to delay-coupled lasers. On the level of the correlation functions, she will present experimental measurements, and show how a simple linear model relates to some fundamental laser characteristics, and reproduces some of the experimentally observed synchronisation patterns. Next she will interpret these synchronisation patterns theoretically in terms of their external cavity modes and their spectrum of Lyapunov exponents.
Dr Otti D'Huys is a Lecturer in Mathematics at Aston University.