Spatio-Temporal Control of Ionization and Electron Dynamics in Laser Plasmas

该项目将探索一种特殊形状的强激光束如何控制等离子体中电子的运动，等离子体是由电子和带电原子组成的气体。一束光可以对物体施加压力，迫使物体运动。通常情况下，这种力太小而看不见，但如果激光束足够亮，物体的重量很轻，就有可能看到这些效应。在这个项目中，我们将研究如何控制激光脉冲的形状，使这种力更容易使电子快速移动。我们还将研究这些激光脉冲是如何在等离子体中产生强波的，在等离子体中，电子和离子被另一个激光脉冲分离。我们的光脉冲非常短（一万亿分之一秒的几分之一），留下的离子没有时间移动。电子在激光脉冲中加速，就像一个冲浪者在一个巨大的水波上，她选择了正确的角度来驾驭波浪。我们希望证明，这可以导致一种新的方法，使电子束的速度接近光速。这项工作还将帮助我们了解如何利用这些激光脉冲制造小通道和眼科手术。它还将向我们展示如何将这些脉冲转换为其他颜色的光。该研究旨在探索利用时空结构的强激光脉冲来控制激光等离子体中的电离和电子动力学。通过控制光束频率分量的横向和角度分布，可以控制脉冲的时空结构。重要的是，角空间啁啾导致相对于传播方向倾斜的强度包络。这使我们能够控制横向群速度，其范围可以从超光速到亚光速。我们将使用这种控制来影响等离子体中电子和波的动力学。在自由电子状态下，我们将测试我们的计算，预测在适当的脉冲前倾斜角度下，电子可以被捕获并被束流的重力动势加速到侧面。这样的配置最终可以用于将电子直接加速到MeV范围，或者单独使用或作为尾流场加速器的光学注入器。在低密度和过密度等离子体状态下，倾斜的脉冲锋可以增强等离子体中波的产生。在后一种情况下，我们将进行一系列实验来探索超快脉冲与表面等离子体波的耦合。我们的项目紧密结合实验、理论和计算建模。实验将在CSM上使用我们的kHz重复率Ti：蓝宝石放大器进行。计算建模将通过开源3D EM PIC程序Epoch和有限元Comsol Multiphysics平台进行。

This project will explore how a specially-shaped intense laser beam can control the movement of electrons in a plasma, a gas of electrons and charged atoms. A beam of light can put pressure on things to force it to move. Normally, this force is too small to see, but if a laser beam is bright enough and the objects have a small weight, it is possible to see these effects. In this project, we will look at how controlling the shape of a pulse of laser light can make it easier for this force to get electrons moving fast. We will also look at how these laser pulses can make strong waves in a plasma, where the electrons and ions become separated by another laser pulse. Our pulses of light are so short (a fraction of a trillionth of a second) that the ions left behind don't have time to move. The electrons accelerate in the laser pulse like a surfer on a big water wave, where she chooses just the right angle to ride the wave. We hope to show that this can lead to a new way to make beams of electrons traveling near the speed of light. The work should also help us understand how we can use these laser pulses for making small channels and for eye surgery. It will also show us how to convert these pulses to other colors of light. The research aims to explore using spatio-temporally structured intense laser pulses to control both ionization and electron dynamics in laser-produced plasmas. By controlling the transverse and angular distribution of the frequency components of the beam, we can control the spatio-temporal structure of a pulse. Important for this project, the angular spatial chirp results in an intensity envelope that is tilted relative to the direction of propagation. This gives us control of the transverse group velocity, which can range from super- to sub-luminal. We will use this control to affect the dynamics of electrons and waves in the plasma. In the free electron regime we will test our calculations that predict that with the proper pulse front tilt angle, electrons can be captured and accelerated to the side by the ponderomotive force of the beam. Such a configuration could ultimately be useful for direct acceleration of electrons to the MeV range, useful on their own or as an optical injector for wakefield accelerators. In the underdense and overdense plasma regime, the tilted pulse fronts can enhance the generation of waves in the plasma. In the latter case, we will perform a series of experiments to explore coupling of ultrafast pulses to surface plasmon waves. Our projects closely couple experiment, theory, and computational modeling. The experiments will be performed at CSM with our kHz repetition rate Ti:sapphire amplifier. Computational modeling will be performed with the open source 3D EM PIC program Epoch and with the finite-element Comsol Multiphysics platform.