Radiation generation via a laser-driven oscillating plasma aperture

高功率激光脉冲的时空和偏振特性的控制是紧凑的基于激光等离子体的粒子加速器和辐射源的发展的核心，其具有广泛的潜在应用。等离子体可以承受极高的能量密度，其光学特性可以在高功率激光脉冲的超快时间尺度上变化，从而实现对强光的动态操纵。该项目建立在我们的工作方案，调查在激烈的激光等离子体相互作用，特别是激光衍射和谐波产生在相对论等离子体孔径相对论光子现象。鉴于我们以前的实验与线偏振光产生束的高能量电子在固定点的光圈，我们现在建议调查使用圆偏振驱动等离子体振荡周围的等离子体光圈的边缘，产生高谐波的基本等离子体频率。理论上预测，当驱动激光器是圆偏振的，高次谐波产生过程有利于基本光的自旋角动量到谐波的固有轨道角动量的转换。实验验证这一点将开辟一个新的领域的可能性，产生强烈的极紫外漩涡，和衍射为基础的高谐波产生在相对论intensity.Central的这种新颖的和使粒子和辐射源技术的发展是控制等离子体中的辐射产生的机制的发展。该项目将探索通过振荡等离子体孔径机制产生高次谐波辐射和光学涡旋的物理学。目标是：1.研究线偏振强激光脉冲与金属箔靶相互作用产生的谐波频谱。研究从线偏振变为圆偏振时产生的谐波频谱的变化3。调查在何种程度上的光谱和空间强度分布的谐波产生的可以通过变化的程度椭圆偏振的激光控制。

Control of the spatial-temporal and polarisation properties of high power laser pulses are central to the development of compact laser-plasma-based particle accelerators and radiation sources, which have wide-ranging potential applications. Plasma can withstand extremely high energy densities and its optical properties can be varied on the ultra fast timescale of a high power laser pulse, enabling dynamic manipulation of intense light. The project builds upon our programme of work investigating relativistic photonic phenomena in intense laser-plasma interactions and specifically laser light diffraction and harmonic generation in a relativistic plasma aperture. Whereas our previous experiments with linearly polarised light generated bunches of high energy electrons at fixed points in the aperture, we now propose to investigate the use of circular polarisation to drive plasma oscillations around the rim of the plasma aperture, to generate high harmonics of the fundamental plasma frequency. It is predicted theoretically that when the driving laser is circularly polarised, the high-harmonic generation process facilitates a conversion of the spin angular momentum of the fundamental light into the intrinsic orbital angular momentum of the harmonics. An experimental verification of this will open up a new realm of possibilities for producing intense extreme ultraviolet vortices, and diffraction-based high harmonic generation at relativistic intensities.Central to the development of this novel and enabling particle and radiation source technology is the development of mechanisms to control radiation generation in plasma. The project will explore the physics of the generation of high harmonic radiation and optical vortices via the oscillating plasma aperture mechanism. The objectives are to:1. Investigate the spectrum of harmonics generated by linearly-polarised intense laser pulses interaction with an ultrathin foil target 2. Investigate changes to the spectrum of harmonics generated when changing from linear to circular polarisation3. Investigate the extent to which the spectral and spatial-intensity distribution of the harmonics generated can be controlled by variation of the degree of ellipticity in the polarisation of the laser light.