Intense visible white-light pulse generation in gas-filled hollow-core fibers pumped by Yb-lasers for multi-color time-resolved spectroscopy

超短、高能激光脉冲在驱动和探测各种材料的超快动力学方面提供了前所未有的能力，如今代表了现代科学众多研究领域的基石。然而，尽管激光频率转换和放大技术已经取得了三十年的进步，但产生能量少周期可见白光（VIS-WL）脉冲（波长：400-800 nm）仍然非常具有挑战性。这种脉冲被认为是研究半导体中生物能量传递过程和光产生的载流子动力学等问题的重要工具。目前的技术通常需要极其复杂的对准和设备，这降低了转换效率并使光束质量恶化。此外，由于所采用的非线性晶体的损伤阈值，在这种系统中最大可实现的脉冲能量是有限的。在这种情况下，充气空心芯光纤（HCF）代表了一个有吸引力的替代非线性平台，因为它们可以容纳高能脉冲，提供直接的光谱扩展，以及出色的输出光束特性。Razzari教授在INRS-EMT的小组最近获得了一个有希望的初步结果，即在镱（Yb）激光脉冲泵浦的HCF中超快VIS-WL脉冲形成。在HCF中深入研究这种新的VIS-WL生成机制并将其开发成可销售的装置是本项目的关键目标。为了实现这些目标，每年将有一个由1名博士生和2名博士后组成的团队，在2名实习生的帮助下，全职从事该项目。这些人员将由Razzari教授监督，并将与我们的工业合作伙伴（few-cycle Inc.）密切互动。最终，我们的合作伙伴公司将能够推出一种经济实惠且可定制的多色系统，依靠工业级Yb激光器来研究各种材料在超快时间尺度上的响应，从而使大量学术和工业实验室能够获得目前仅在世界上少数顶尖研究中心可用的技术。

Ultrashort, high-energy laser pulses have delivered unprecedented capabilities in driving and probing ultrafast dynamics in various materials and nowadays represent the cornerstone of a multitude of research fields in modern science. However, despite the three decades of progress of laser frequency conversion and amplification technology, the generation of energetic few-cycle visible white light (VIS-WL) pulses (wavelength: 400-800 nm) is still very challenging. Such pulses are regarded as an essential tool for the temporal investigation of e.g., biological energy transfer processes and photo-generated charge carrier dynamics in semiconductors. Current technology typically requires extremely complex alignment and apparatus that lower the conversion efficiency and deteriorate the beam quality. Also, the maximum achievable pulse energy is limited in such systems, due to the damage threshold of the employed nonlinear crystals. In this context, gas-filled hollow-core fibers (HCF) represent an appealing alternative nonlinear platform, as they accommodate high-energy pulses and provide a straightforward spectral extension, together with excellent output beam characteristics. Prof. Razzari's group at INRS-EMT has recently obtained a promising preliminary result of ultrafast VIS-WL pulse formation in an HCF pumped by ytterbium (Yb) laser pulses. The thorough investigation of this novel VIS-WL generation mechanism in an HCF and its exploitation into a marketable setup are the key target of this project. To achieve these goals, an overall team of 1 PhD student and 2 postdocs, helped by 2 intern students every year, will work on the project full time. These personnel will be supervised by Prof. Razzari and will closely interact with our industrial partner (few-cycle Inc.). Eventually, our partner company will be able to introduce an affordable and customizable multi-color system relying on an industrial-grade Yb laser to study the response of a variety of materials on ultrafast time-scales, thus allowing a large number of academic and industrial labs to have access to a technology currently available only in a handful of top-notch research centers around the world.