Particle-in-cell study of the time evolving focal characteristics of relativistic plasma mirrors

We perform a particle-in-cell study of a relativistic intensity laser beam incident onto a plasma mirror to characterize the focusing properties of the target. We first perform studies with semi-infinite pulses and track the changing focal properties of the mirror for several different target densities and compositions; we explore this evolution’s dependencies on various plasma parameters and isolate the role of ion mobility. One must track the relativistically modified critical density in the target and its deformation throughout time. Following this, we perform more realistic ultra-short pulse simulations to better understand the changing mirror properties on the timescales characteristic of these systems.