Nonlinear Optics and Dynamics of Relativistically Transparent Plasmas

．在中等光强下，人们很好地理解了光学的基本性质。然而，在使用最先进的激光器能够产生的最高强度下，出现了许多新的和有用的光学现象。当高强度激光脉冲聚焦在介质上时，它会产生等离子体，并能驱动极端温度和强烈的电场和磁场。这就产生了具有独特性质的高能粒子和辐射束，为科学和新应用开辟了新的领域。等离子体电子在强激光场中以接近光速的速度振动，这改变了等离子体的基本特性，比如它的折射率。粒子运动和非线性光学性质随激光脉冲的相互作用而动态演化，这意味着等离子体可以作为有源光学元件。如果加以利用，这将为研究人员提供一种工具来动态控制超强激光的特性，以及产生的带电粒子束和辐射。在控制电子对在低密度（透明）等离子体中传播的强激光脉冲的集体响应方面取得了重大进展，从而在低发散光束中产生高能量、超短电子束。在固体密度等离子体的情况下，情况更为复杂，例如用于离子加速和高谐波产生。密集的等离子体就像一面镜子（等离子体镜），反射了相当一部分激光束。然而，在超高激光强度下，等离子体电子的非线性运动导致相对论光学现象，使致密等离子体透明。我们的研究重点是在超薄薄膜中探索相对论等离子体光学。这些目标最初作为等离子体反射镜，反射激光，并在相互作用的过程中演变为相对透明。这种瞬态行为为控制致密等离子体中的带电粒子加速提供了一条很有前途的途径。在相互作用的不透明阶段，产生强烈的纵向静电场，产生正向的电子束和离子束，这可以利用激光在透明期间通过目标传播时引起的相对论光学效应来控制。我们将研究这种方法作为一种动态控制传输的强激光和由此产生的高能粒子和辐射的基本特性的手段。我们将利用苏格兰等离子体加速器应用中心的新型350 TW激光器的互补能力，其中新技术可以随着时间的推移而开发和优化，以及中央激光设施的双子座和火神激光器，它们提供更高的功率和双光束能力。我们还将使用高性能计算机进行紧密耦合模拟。这将使我们能够研究发展相对论等离子体光学过程的潜力，以动态控制超强激光脉冲的空间、时间和偏振特性。我们将研究使用这种方法来控制高能粒子束和相互作用中产生的辐射的性质。与我们在捷克共和国和罗马尼亚的下一代极端光基础设施激光设施的国际合作伙伴一起，我们还将研究超高强度下的相对论光学和等离子体动力学物理学，为此高场过程将改变基础物理学。我们将清楚地了解超高强度光学过程，它们在开发等离子体光学和光子器件以及致密等离子体中粒子和辐射产生的动态控制方面的潜在应用。

.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..