Design of transient plasma photonic structure mirrors for high-power lasers using deep kernel Bayesian optimisation.

Ultra-high power lasers are becoming important tools for advancing high-field physics and fusion research. However, their development is constrained by the damage thresholds of conventional optical components; it is challenging to design optical elements capable of withstanding high powers without them becoming impractically large. Here we show that transient plasma photonic structures, formed by the interaction of intercepting laser pulses in gas, can act as compact and robust reflective elements. Because these structures evolve in space and time, and rely on many interdependent parameters, designing optical components using traditional trial-and-error design methods is challenging. We show that machine learning can efficiently explore this complex parameter space to rapidly design robust, high reflectivity plasma mirrors. Moreover, this design process unexpectedly discovers a regime where unchirped laser pulses are compressed. This work demonstrates machine learning as a powerful tool for design, discovery and development of ultra-compact optical components for next-generation lasers.