Plasmas created by extreme ultraviolet lasers

20世纪60年代早期激光的发明导致了高功率(&gt；百万瓦)红外和可见光脉冲激光聚焦到固体目标上，以产生热(&gt；50万开尔文)等离子体的实验。在近50年的研究中，激光相互作用的物理、羽流膨胀的物理以及许多重要的应用都得到了较为详细的阐述。当聚焦在固体目标上时，可见/红外激光在大部分脉冲持续时间内不会穿透固体，而是以比固体密度小100-1000倍的密度被膨胀的等离子体羽流吸收。然而，将激光波长投放到极端紫外线(EUV)中，使激光能够穿透固体，并以固体密度直接产生等离子体。PI进行的初步模拟研究表明，极紫外激光辐射与大多数固体目标的相互作用将导致不透明度迅速下降(从而使目标“漂白”)。首先漂白EUV光子能量的衰减长度，然后再漂白另一个衰减长度，从而在亚纳秒的时间尺度上通过固体目标传播“漂白波”。与相同脉冲能量和焦斑直径的红外或可见光辐射相比，有效烧蚀的靶材数量要大得多。由于缺乏足够能量(&gt；10微焦耳)的实验室EUV激光器用于实验，因此几乎没有进行建模工作来阐明对EUV激光产生的等离子体的理解。然而，科罗拉多州立大学(CSU)已经开发出工作在波长46.9 nm(光子能量26.4 eV)、产生高达1毫焦耳/脉冲、峰值功率为100万瓦的可靠毛细管放电激光器。我们建议开发模拟模型来解释EUV激光产生的等离子体的发射光谱和质谱计结果。我们将使用约克大学的高功率红外激光器测试光谱仪诊断，并与CSU合作进行光谱和质谱仪测量，以便与模拟模型进行比较。一种新的激光产生的等离子体将被研究，在研究热致密物质、激光切割和烧蚀以及与每年700亿美元相关的固体材料光刻方面具有潜在的影响。与微电子机械系统(MEMS)制造相关的收入行业。

The invention of the laser in the early 1960s led to experiments where high power (> million Watts) infra-red and visible pulsed lasers were focused onto solid targets in order to produce hot (> 0.5 million degrees Kelvin) plasmas. In almost 50 years of study, the physics of the laser interaction, the physics of the expanding plume and many important applications have been elucidated in some detail. When focussed onto solid targets, visible/infra-red lasers do not penetrate to the solid for most of the pulse duration, but are absorbed in the expanding plasma plume at densities 100- 1000 times smaller than the solid density. Dropping the laser wavelength into the extreme ultra-violet (EUV), however, enables the laser to penetrate into the solid and to create plasma directly at the solid density. Initial modelling studies that have been undertaken by the PI show that the interaction of EUV laser radiation with most solid targets will cause a rapid drop in opacity (so that the target 'bleaches'). Initially an attenuation length for the EUV photon energy is bleached and then another attenuation length, so that a 'bleaching wave' propagates through the solid target on a sub-nanosecond timescale. A much more massive amount of target material is effectively ablated than can occur with infra-red or visible radiation of the same pulse energy and focal spot diameter. Little modelling work has been undertaken to elucidate understanding of EUV laser-produced plasmas because of the lack of sufficiently energetic (> 10 microJoules) laboratory EUV lasers for experiments. However, reliable capillary discharge lasers operating at wavelength 46.9 nm (photon energy 26.4 eV) producing up to 1 milliJoule/pulse and peak powers of a million Watts have been developed at the Colorado State University (CSU). We propose to develop simulation models to interpret emission spectra and mass spectrometer results from EUV laser produced plasmas. We will test spectrometer diagnostics using the University of York high power infra-red laser and in collaboration with CSU make spectral and mass spectrometer measurements for comparison to the simulation models. A new class of laser-produced plasma will be studied with potential impact in the study of warm dense matter, laser cutting and ablation and solid material lithography with relevance to the $70B p.a. revenue industry associated with the manufacture of microelectromechanical systems (MEMS).