标题： 全光飞秒钟用于成像隧穿波包 显示英文标题

标题： All-optical attoclock for imaging tunnelling wavepackets

摘要： 最近在测量冷原子通过光学创建的势垒隧穿过程中的时间延迟的实验重新引发了关于光诱导电子从原子隧穿过程中可能的时间延迟的有争议的辩论。 有有力的理论和实验论点被提出以支持相反的观点，确认或反驳有限隧穿时间延迟的存在。 然而，这种延迟，无论是否存在，只是表征隧穿波包的一个单一量；其背后的动力学更加丰富。 在这里，我们建议在激光诱导隧穿中的光电探测中增加对隧穿电子发出的光的探测——即所谓的布鲁内尔辐射。 使用单色和双色驱动场的组合，我们识别了当隧穿波包从隧穿势垒中出现并远离核心时重新塑造的全光学特征。 这种重塑不仅包括有效的时间延迟，还包括电离过程的时间反演不对称性，我们从理论上描述并实验上观察到了这一点。 我们展示了延迟和重塑如何映射到布鲁内尔辐射的偏振特性上，不同谐波表现出如钟表的不同指针以不同速度移动。 全光学检测为在凝聚态系统中时间分辨光学隧穿铺平了道路，例如在固体中跨越带隙的隧穿，在阿托秒时间尺度上。 显示英文摘要

摘要： Recent experiments on measuring time-delays during tunnelling of cold atoms through an optically created potential barrier are reinvigorating the controversial debate regarding possible time-delays during light-induced tunnelling of an electron from an atom. Compelling theoretical and experimental arguments have been put forward to advocate opposite views, confirming or refuting the existence of finite tunnelling time delays. Yet, such a delay, whether present or not, is but a single quantity characterizing the tunnelling wavepacket; the underlying dynamics are richer. Here we propose to augment photo-electron detection in laser-induced tunnelling with detection of light emitted by the tunnelling electron -- the so-called Brunel radiation. Using a combination of single-color and two-color driving fields, we identify the all-optical signatures of the re-shaping of the tunnelling wavepacket as it emerges from the tunnelling barrier and moves away from the core. This reshaping includes not only an effective time-delay but also time-reversal asymmetry of the ionization process, which we describe theoretically and observe experimentally. We show how both delay and reshaping are mapped on the polarization properties of the Brunel radiation, with different harmonics behaving as different hands of a clock moving at different speeds. The all-optical detection paves the way to time-resolving optical tunnelling in condensed matter systems, e.g. tunnelling across bandgaps in solids, on the attosecond time-scale.