MRI: Development of a Phase-coherent Laser System for Attosecond Science and Precision Spectroscopy

[0722800]保罗斯自从近半个世纪前激光被发明以来，激光物理学沿着两条看似不同的道路发展。研制出了短脉冲、宽频谱带宽的高功率激光器，用于原子分子动力学研究；研制出了窄带宽的连续激光器，用于高分辨率光谱学研究。频率梳技术——由Hall和Hansch发明并获得2005年诺贝尔物理学奖的认可——将这些路径重新结合在一起，并为精密光谱学和动力学实验开辟了新的机会，这也是该项目的主题。频率梳技术可以产生由几个精确控制相位的光学周期组成的激光脉冲，或者相当于一组精确定义频率的紧密间隔的颜色。该技术能够以亚周期精度控制激光场的时间演变，从而获得阿秒时域。阿秒（十亿分之一秒的十亿分之一）时域是电子在原子和分子中运动的自然时间尺度。因此，阿秒照明使得拍摄电子动力学快照成为可能，例如在化学反应中。直到最近才有可能产生阿秒激光脉冲，这一发展对原子和分子物理学、化学和生物学都具有根本性的重要性。该项目将开发一种多功能相位相干激光系统，使德克萨斯a&m大学的阿秒激光物理研究和教育成为可能。该系统的核心将由一个高功率啁啾脉冲光参量放大器组成，该放大器能够在红外光谱区域产生相位稳定的少周期脉冲。这种脉冲将在强场激光物理实验中充当探针。此外，它们将允许产生与驱动光场完全同步的孤立的极紫外（XUV）辐射阿秒脉冲。同时可用的相位稳定的少周期红外脉冲和同步XUV脉冲将为探索分子解离和分子排列的阿秒动力学提供能力。此外，利用分子振动和同步旋转的独特特性的各种想法将得到测试。该系统将成为德州农工大学科学与工程学院和学生的宝贵资源。该项目将为研究生和本科生提供良好的培训机会，并将为相参激光系统、XUV技术和超快光学的无数应用培养必要的劳动力。计划与美国和欧洲的顶尖科学家合作，将为学生提供宝贵的国际经验。该项目的结果将通过科学出版物、学术讨论会和教师和学生的会议报告来传播。推广活动，如暑期学校、系列讲座、科学主题日，将用于推广该项目，吸引最优秀的学生，并告知感兴趣的公众。

0722800PaulusSince the original invention of the laser nearly half a century ago, laser physics has evolved on two seemingly divergent paths. High power lasers with short pulses and broad spectral bandwidths were developed for use studying atomic and molecular dynamics and continuous lasers with very narrow bandwidths were developed and used in high-resolution spectroscopy. The frequency comb technique - invented by Hall and Hansch and recognized by the 2005 Physics Nobel prize - brought the paths back together and opened new opportunities for precision spectroscopy and dynamics experiments, the theme of this project. The frequency-comb technique allows production of laser pulses that consist of only a few optical cycles with the phase being precisely controlled, or equivalently a set of closely spaced colors with precisely defined frequency. The technique enables control of the temporal evolution of the laser field with sub-cycle precision thus giving access to the attosecond time domain. The attosecond (a billionth of a billionth of a second) time domain is the natural time scale of electron motion in atoms and molecules. Therefore, attosecond illumination makes it possible to take snapshots of electron dynamics, e.g. in chemical reactions. Only very recently has it become possible to generate attosecond laser pulses, a development of fundamental importance for atomic and molecular physics, for chemistry and for biology.This project will develop a versatile phase-coherent laser system that will enable research and education in attosecond laser physics at Texas A&M University. The core of this system will consist of a high-power chirped-pulse optical parametric amplifier capable of generating phase-stabilized few-cycle pulses in the infrared (IR) spectral region. Such pulses will serve as probes in strong-field laser physics experiments. Furthermore, they will allow production of isolated attosecond pulses of extreme ultraviolet (XUV) radiation which are perfectly synchronized with the driving optical field. Simultaneous availability of phase-stabilized few-cycle IR pulses and synchronized XUV pulses will provide capabilities for exploring the attosecond dynamics of molecular dissociation and molecular alignment. In addition, various ideas exploiting unique properties of molecules vibrating and rotating in lockstep will be tested. The system will serve as a valuable resource to a large number of Texas A&M science and engineering faculty and students.The project will offer excellent training opportunities to graduate and undergraduate students, and will train the workforce necessary for the countless applications of phase-coherent laser systems, XUV technology, and ultra-fast optics in general. The planned collaborations with leading scientists in the US and Europe will provide the students with valuable international experience. The results of this project will be disseminated through scientific publications, colloquia, and conference presentations by faculty and students. Outreach activities such as summer schools, lecture series, science-themed days will be used to promote the project, attract the best students, and inform the interested public.