Nonlinear Optics and Dynamics of Relativistically Transparent Plasmas

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.The fundamental properties of optics are well understood at moderate light intensities. However, at the highest intensities capable of being produced using state-of-the-art lasers, many new and useful optical phenomena arise. When a high intensity laser pulse is focused onto a medium it generates a plasma and can drive extreme temperatures and intense electric and magnetic fields. This results in the production of beams of high energy particles and radiation with unique properties, which are opening up new frontiers in science and new applications. The plasma electrons quiver in the intense laser field at velocities close to the speed of light, which changes fundamental properties of the plasma, such as its refractive index. The fact that the particle motion and nonlinear optical properties dynamically evolve in response to inter-action with the laser pulse means that the plasma can act as an active optical element. If harnessed, this would provide researchers with a tool to dynamically control both the properties of ultraintense laser light and the beams of charged particles and radiation produced. Great progress has been made in controlling the collective response of electrons to intense laser pulses propagating in low density (transparent) plasma, resulting in the production of high energy, ultrashort bunches of electrons in a low divergence beam. The situation is more complex in the case of solid density plasma, used for example for ion acceleration and high harmonic generation. The dense plasma acts as a mirror (a plasma mirror), which reflects a significant portion of the laser beam. At ultrahigh laser intensities, however, the nonlinear motion of the plasma electrons results in relativistic optical phenomena which can render the dense plasma transparent.Our proposed research focuses on exploring relativistic plasma optics in ultrathin foils. Such targets initially act as a plasma mirror, reflecting laser light, and evolve over the course of the interaction to become relativistically transparent. This transient behaviour offers a promising route to controlling charged particle acceleration in dense plasma. During the opaque phase of the interaction, strong longitudinal electrostatic fields are generated, resulting in forward-directed electron and ion beams, which can be controlled using relativistic optical effects induced as the laser propagates through the target during transparency. We will investigate this approach as a means of dynamically controlling fundamental properties of the transmitted intense laser light and the resulting high energy particles and radiation.We will use the complementary capabilities of the new 350 TW laser at the Scottish Centre for the Applications of Plasma Accelerators, in which new techniques can be developed and optimised over time, and the Gemini and Vulcan lasers at the Central Laser Facility, which offer higher power and dual beam capability. We will also perform closely coupled simulations using high performance computers. This will allow us to investigate the potential for developing relativistic plasma optics processes for the dynamic control of the spatial, temporal and polarisation properties of ultraintense laser pulses. We will investigate the use of this approach for controlling the properties of beams of high energy particles and radiation produced in the interaction. Together with our international partners at the next-generation extreme light infrastructure laser facilities in the Czech Republic and Romania, we will also investigate the physics of relativistic optics and plasma dynamics at ultrahigh intensities, for which high field processes will modify the underpinning physics. We will develop a clear understanding of ultrahigh intensity optical processes, their potential use in developing plasma optical and photonic devices and the dynamic control of particle and radiation production in dense plasma..