Attosecond Electron Synchrotron on a Nanoscale

强激光可能会将大粒子加速器的一些科学和应用带到一个中等规模的实验室，使其能够为更多科学和技术领域的更广泛的研究人员和用户所用。从辐射物理学的角度来看，激光的一个优势是它们能够产生前所未有的短(阿秒)紫外线和X射线辐射脉冲。尽管空间尺度有很大不同，但大规模同步加速器设施(X射线结晶学和材料科学研究的主要研究工具)中的电子发射和在极强光场影响下在固体表面加速的电子的物理发射在本质上是相同的。强烈的超短脉冲光与固体的相互作用导致目标电离，并瞬间形成类似纳米尺寸的“同步加速器”的东西(带电粒子在比驱动光场的半周期短得多的时间间隔内发射高能辐射脉冲)。这一过程可以通过入射光场波形随时间演化的细节来控制。本计划的目的是利用专门准备的激光场来驯服固体中的同步加速器型电子轨迹，并确保发射出强烈的紫外线和X射线辐射。本计划将探索通过对驱动激光脉冲波形的亚周期整形来提高极端光场下固体的相干紫外线和X射线发射强度的可能性。波形整形可以通过将激光器的基频与其二次谐波或更高频率分量混合来实现。研究了驱动场中不同颜色的能量分布以及它们之间的相位延迟对辐射光谱的影响。该计划将寻求驱动波形的优化解决方案，以及对过程效率的物理限制。这项研究可能会为激光产生的固体密度等离子体中场控制电子振荡的动力学提供新的见解。最终，这种方法可能提供比目前实现的更高的阿秒脉冲强度，打开一条将超快计量学推向时间分辨X射线泵浦-探测光谱学的途径。

Intense laser light may bring some of the science and applications of large particle accelerators down to a moderate-size laboratory, making it accessible to a broader range of researchers and users in multiple fields of science and technology. From the radiation physics perspective, an advantage of lasers is their ability to generate unprecedentedly short (attosecond) pulses of ultraviolet and x-ray radiation. Even though the spatial scales are drastically different, the physics of emission by electrons in large-scale synchrotron facilities (major research tools for x-ray crystallography and materials science research) and by electrons undergoing acceleration at the surface of a solid under the influence of extreme-intensity light fields are, in an essential way, the same. The interaction of intense, ultrashort-pulsed light with solids results in target ionization and the momentary formation of something akin to a nanometer-sized "synchrotron" (the charged particles emit bursts of high-energy radiation within time intervals much shorter than the half-cycle of the driving light field). This process can be controlled by the details of how the incident light field waveforms evolve with time. Taming synchrotron-type electron trajectories in solids by specially prepared laser fields, and ensuring that the result is the emission of intense ultraviolet and x-ray radiation is the aim of this program.This program will explore the chance to enhance the intensity of coherent ultraviolet and x-ray emission from solids under extreme light fields by sub-cycle shaping of the driving laser pulse waveforms. The waveform shaping can be achieved through mixing the laser fundamental frequency with its second harmonic or higher frequency components. The effect of the energy distribution of different colors in the driving field as well as the phase delay between them on the radiation spectra will be studied. The program will seek the optimized solutions for driving waveforms, as well as the physical limits on the efficiency of the process. This study may provide new insight into the dynamics of field-controlled electron oscillations in laser-produced solid-density plasmas. Ultimately, this approach may offer higher attosecond pulse intensities than those currently achieved, opening a pathway to advance ultrafast metrology toward time-resolved x-ray pump-probe spectroscopy.