MRI: Acquisition of a High Intensity Tunable Femtosecond Laser.

MRI：获取高强度可调谐飞秒激光。

• 批准号: 1229674
• 负责人: Carlos Trallero
• 金额: $ 69.29万
• 依托单位: Kansas State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1229674&HistoricalAwards=false
• 关键词: MRI; Acquisition; Intensity; Tunable; Femtosecond

This NSF-MRI allows generating milli-Joule (mJ) level, few-cycle pulses (10 fs to 14 fs) in the mid-infrared (1400-2200 nm) spectral region that are carrier-envelope phase stable. To generate these pulses, a white-light seeded optical parametric amplifier (OPA) is pumped by a 20 mJ femtosecond laser. The pulses emerging from the OPA are then spectrally broadened and compressed. Such capabilities are at the forefront of current ultrafast physics and attosecond science, opening a window for new and exciting studies in the general area of laser-matter interaction.Extending these pulses to the mid-IR should enhance high-harmonic generation -- an effort presently pursued at just a handful of laboratories around the world. Driving the harmonics with these longer wavelengths will lead to a higher photon flux and energy. This high photon flux is critical for studies of non-linear UV/XUV phenomena as well as for extending our studies to the more complex systems of interest for most applications. The longer wavelength driving laser will also enable the investigation of electronic dynamics using a very different, rather unorthodox, approach. Namely, by taking advantage of the fact that dissociation in some molecules is an almost perfect analog of ionization in atoms, only few femtosecond laser pulses are required since nuclei move much slower than electrons. These pulses must, however, have long wavelengths to produce a measurable signal. In addition to the science advances, technological advances such as shaping attosecond pulses to eliminate their natural chirp or tailoring them to drive specific dynamics will be pursued. Such capabilities would be a substantial accomplishment and would, in turn, enable further scientific advances since scientific and technological breakthroughs go hand-in-hand in this field.Measuring the dynamics of and controlling electrons in matter are major themes that extend throughout much of atomic, molecular and optical (AMO) physics, chemistry, materials science, and even biology today. In fact, the first of the five "Grand Challenges for Basic Energy Science," as identified in the Department of Energy's special BESAC report in 2007, is "How do we control material processes at the level of electrons?" This theme appeared again in the National Research Council's "Physics 2010" report where the AMO contribution was entitled "Controlling the Quantum World." To accomplish these goals, laser pulses on the order of tens of attoseconds (1 as = 10^-18 s) are required. Such pulses are a challenge to produce, but by using high-harmonic generation (HHG), pulses below 100 as have been obtained in a few leading labs around the world, including here at the J. R. Macdonald Laboratory (JRML). This technological breakthrough has given birth to the field of attosecond science, which is presently one of the hottest in AMO physics. This project will employ these attosecond UV/XUV pulses to study atomic and molecular dynamics as well as to probe more complex condensed matter systems. In addition, by observing the HHG spectra and/or emitted electrons, structural changes in molecules can be observed as they happen, deepening our understanding of the underlying dynamics and thereby taking an important step in controlling chemical reactions at the quantum mechanical level.Beyond the technical and scientific impacts, this grant significantly impacts a large number of young scientists through hands-on training of the roughly seven postdocs, sixteen graduate students, and five undergraduate students hosted by the JRML. While the training opportunities mainly benefit graduate students and postdoctoral fellows, they also have an impact on undergraduate students through, for instance, the Physics Department's Research Experiences for Undergraduates (REU) program funded by the NSF. However, this laser source has also created a very broad collaboration between participants from institutions in three EPSCoR states who are currently funded primarily by NSF and DOE. The institutions involved are Kansas State University, Louisiana State University, Augustana College (an undergraduate institution in South Dakota), and the University of Kansas. The JRML group will leverage this new laser system to initiate additional collaborations following this model.

这种NSF-MRI允许在中红外(1400-2200 nm)光谱区域产生毫焦耳(MJ)级、少周期脉冲(10f至14f)，这些脉冲是载波包络相位稳定的。为了产生这些脉冲，用20mJ的飞秒激光泵浦白光种子光参量放大器(OPA)。然后从OPA中出现的脉冲被频谱展宽和压缩。这种能力处于当前超快物理和阿秒科学的前沿，为激光与物质相互作用的一般领域的新的和令人兴奋的研究打开了一扇窗。将这些脉冲扩展到中红外应该会增强高次谐波的产生--目前世界上只有几个实验室在进行这一努力。用这些更长的波长驱动谐波将导致更高的光子流量和能量。这种高的光子通量对于研究非线性UV/XUV现象以及将我们的研究扩展到大多数应用中感兴趣的更复杂的系统是至关重要的。更长波长的驱动激光也将使人们能够使用一种非常不同的、相当非正统的方法来研究电子动力学。也就是说，利用一些分子中的解离几乎完全类似于原子中的电离这一事实，只需要很少的飞秒激光脉冲，因为原子核的运动比电子慢得多。然而，这些脉冲必须有很长的波长才能产生可测量的信号。除了科学进步外，还将追求技术进步，如塑造阿秒脉冲以消除其自然啁啾，或对其进行定制以驱动特定的动力学。这样的能力将是一项实质性的成就，反过来将使科学进一步进步，因为科学和技术突破在这一领域是齐头并进的。测量和控制物质中电子的动力学是贯穿当今原子、分子和光学(AMO)物理、化学、材料科学甚至生物学的主要主题。事实上，能源部2007年在BESAC的特别报告中确定的五大基础能源科学挑战中的第一个是“我们如何在电子水平上控制材料过程？”这一主题再次出现在国家研究委员会的《物理2010》报告中，其中AMO的贡献题为《控制量子世界》。为了实现这些目标，需要几十阿秒(1AS=10^-18 S)量级的激光脉冲。这类脉冲的产生是一个挑战，但通过使用高次谐波产生(HHG)，100以下的脉冲已经在世界各地的几个领先实验室获得，包括J·R·麦克唐纳实验室(JRML)。这一技术突破催生了阿秒科学领域，这是目前AMO物理学中最热门的领域之一。这个项目将使用这些阿秒UV/XUV脉冲来研究原子和分子动力学，以及探测更复杂的凝聚态系统。此外，通过观察HHG光谱和/或发射的电子，可以在发生时观察到分子结构的变化，加深我们对潜在动力学的理解，从而在量子力学水平上控制化学反应方面迈出重要的一步。除了技术和科学影响之外，这项拨款通过对JRML主办的大约7名博士后、16名研究生和5名本科生的动手培训，显著影响了大量年轻科学家。虽然培训机会主要受益于研究生和博士后研究员，但它们也对本科生产生了影响，例如，通过国家科学基金会资助的物理系本科生研究体验(REU)项目。然而，这种激光光源也在来自三个EPSCoR州的机构的参与者之间建立了非常广泛的合作，这些机构目前主要由NSF和能源部提供资金。涉及的机构包括堪萨斯州立大学、路易斯安那州立大学、奥古斯塔纳学院(南达科他州的一所本科院校)和堪萨斯大学。JRML小组将利用这一新的激光系统来启动遵循这一模式的更多合作。