Waveform Synthesis of Attosecond Optical Pulses: A Common Route to Attosecond Pump-Probe Spectroscopy and Nanoscopy in Aqueous Solution

阿秒光脉冲的波形合成：水溶液中阿秒泵浦探针光谱学和纳米显微镜学的共同途径

• 批准号: RGPIN-2015-06208
• 负责人: BeaudoinBertrand, Julien
• 金额: $ 2.4万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=644886
• 关键词: Waveform; Synthesis; Attosecond; Optical; Pulses

When a molecule absorbs light, its electronic cloud reacts almost instantaneously followed by rovibrational nuclear dynamics on the femtosecond (fs=10-15s.) to picosecond (ps=10-12s.) timescale. In photosynthesis, for example, the absorption of ultraviolet light by chlorophyll molecules induces an electronic dipole oscillation, which has a period in the range of 1 fs, followed by its slower decay and energy redistribution to the nuclear degrees of freedom. Over the last decades, time-resolved spectroscopy showed how few-cycle femtosecond laser pulses can be used to steer nuclear wave packets and control the outcome of elementary reactions. The lack of shorter pulses, however, has left control of the electron wave packets on the sub-oscillation period timescale unexplored. Would it be possible to follow and, ultimately, more efficiently control reaction dynamics right from the earliest moments when electron dipole forces initiate nuclear motion?****The emerging field of Attosecond Physics offers a new take on these questions. In fact, both isolated extreme ultraviolet (XUV, 10-100 eV) and broadband optical attosecond (as=10-18 s.) pulses can be simultaneously produced and synchronized with common tabletop femtosecond optical technology. Recent laser developments even extend the attosecond emission from the XUV to "water window" soft X-rays (280-500eV) and beyond. This feat radically departs from the shortest picosecond pulses so far only available from large scale (0.1-10 km) accelerator facilities. The water window designates the spectral range where water is essentially transparent to the radiation while carbon and nitrogen atoms are highly absorptive; enabling novel high-contrast, element-specific, time-resolved spectroscopy and nanoscopy in water. Combining my experience in time-resolved molecular spectroscopy (Ph.D, University of Ottawa, director: Paul Corkum) with a unique -in Canada- expertise in attosecond technology and optical waveform synthesis (Banting postdoctoral fellowship at the Max-Planck-Institut for Quantum Optics in Munich, 2013-2014, director: Ferenc Krausz), my research group has the long term vision:***To make possible the spectroscopy of biomolecules in aqueous solution with unexplored time and spatial resolutions through the implementation of optical waveform synthesis providing both optical and water window soft X-ray attosecond pulses.***By the end of year 5, we will have:***1) Demonstrated optical waveform synthesis to generate coherent soft X-ray water window radiation. ***2) Used this radiation for the spectroscopy of molecules in aqueous phase in unexplored attosecond regime.***3) Used the ultrashort wavelength of coherent soft X-rays (2-10 nm) to spatially resolve nanometric structures.***This interdisciplinary research will train highly qualified personnel and open avenues for new technological applications in health sciences.*** *** *** **

当分子吸收光时，它的电子云几乎瞬间反应，然后是飞秒（fs=10- 15 s）的振转核动力学。皮秒（ps=10- 12 s.）时间尺度。例如，在光合作用中，叶绿素分子对紫外光的吸收引起电子偶极振荡，其周期在1 fs范围内，随后是其较慢的衰减和能量重新分配到核自由度。在过去的几十年里，时间分辨光谱学展示了如何使用几个周期的飞秒激光脉冲来控制原子核波包和控制基元反应的结果。然而，缺乏较短的脉冲，留下了控制的电子波包上的子振荡周期的时间尺度未探索。是否有可能从电子偶极力引发核运动的最早时刻起就跟踪并最终更有效地控制反应动力学？*阿秒物理学的新兴领域为这些问题提供了新的解决方案。实际上，无论是孤立极紫外（XUV，10-100 eV）还是宽带光学阿秒（as=10-18 s.）脉冲可以同时产生，并且与普通桌面飞秒光学技术同步。最近的激光发展甚至将阿秒辐射从XUV扩展到“水窗”软X射线（280- 500 eV）和更高。这一壮举从根本上背离了迄今为止只有大规模（0.1-10公里）加速器设施才能提供的最短皮秒脉冲。水窗口指定了水对辐射基本上透明而碳和氮原子具有高度吸收性的光谱范围;从而实现了水中的新型高对比度、元素特异性、时间分辨光谱和纳米显微镜。结合我在时间分辨分子光谱学方面的经验（渥太华大学博士，主任：Paul Corkum）在阿秒技术和光学波形合成方面拥有加拿大独一无二的专业知识（2013-2014年，在慕尼黑的马克斯普朗克量子光学研究所担任博士后，主任：Ferenc Krausz），我的研究小组有一个长期愿景：* 通过实施光学波形合成，提供光学和水窗软X射线阿秒脉冲，使水溶液中生物分子的光谱学具有未知的时间和空间分辨率成为可能。到第五年年底，我们将有：*1）演示光学波形合成，以产生相干软X射线水窗辐射。*2）在未探索的阿秒状态下，将该辐射用于水相中分子的光谱学。* 3)使用相干软X射线的超短波长（2-10 nm）空间分辨纳米结构。*这项跨学科的研究将培养高素质的人才，并为健康科学的新技术应用开辟道路。*** *** **