Ultrafast microscale platform simulates complex delay-coupled systems

Physicists at the University of Southampton are studying the behaviour of exciton-polariton quasiparticles to help understand and predict the dynamics of delay-coupled networks seen in many different areas of science and technology.

Researchers have developed an ultrafast microscale platform to investigate the nature of interactions between two spatially separated condensates of exciton-polaritons in microcavities.

The technique simulates dynamics similar to time-delayed real-world systems that are important in fields such as communication networks, infectious diseases spread, road traffic and financial markets.

Exciton-polaritons are half-light, half-matter quasiparticles that can undergo a power-driven phase transition to a macroscopically coherent state similar to the principles of a laser, but with the addition of strong intrinsic non-linearities of their excitonic component.

Recent experiments from an international research collaboration, published in Nature’s Communications Physics journal, have demonstrated controllable tuning between steady state (single-colour) and limit-cycle (two-colour) regimes of the two coupled condensate system that can be explained through time-delayed equations of motion.

Imaging of the system’s photoluminescence revealed interference fringes in-between the two condensates as a result of two radially expanding matter-wave sources, similar to the rippled formed when two stones are thrown at different locations into a lake.

Julian Töpfer, article co-author, says: “Our work shows that networks and lattices of ballistically coupled polariton condensates have the potential to open an optical-based platform to study and simulate complex delay-coupled systems.

“With this new knowledge on interactions between ballistic polariton condensates, the next logical step is to start building more complicated structures composed of multiple condensates aimed at either optical computation strategies, or to study emergent phenomena in networks of nonlinear optical oscillators.”

Experiments have been conducted at Southampton by Julian, Dr Lucy Pickup and Professor Pavlos Lagoudakis, with theory and simulations assessed by Dr Helgi Sigurdsson.