Twisting attosecond pulse trains by amplitude-polarization IR pulses

Abstract

Natively, atomic and molecular processes develop in a sub-femtosecond time scale. In order to, for instance, track and capture the electron motion in that scale we need suitable 'probes'. Attosecond pulses configure the most appropriate tools for such a purpose. These ultrashort bursts of light are generated when a strong laser field interacts with matter and high-order harmonics of the driving source are produced. In this work, we propose a way to twist attosecond pulse trains. In our scheme, each of the attosecond pulses in the train has a well-defined linear polarization, but with a different polarization angle between them. To achieve this goal, we consider an infrared pulse with a particular polarization state, called amplitude polarization. This kind of pulse was experimentally synthesized in previous works. Our twisted attosecond pulse train is then obtained by nonlinear driving an atomic system with that laser source, through the high-order harmonics generation phenomenon. We reach a high degree of control in the polarization of the ultrashort coherent XUV-generated radiation. Through quantum mechanical simulations, supplemented with signal processing tools, we are able to dissect the underlying physics of the generation process.We are confident these polarized-sculpted XUV sources will play an instrumental role in future pump-probe-based experiments. Classical electrodynamics and quantum mechanics are the fundamental building blocks for the description of many natural phenomena. By measuring the wavelength and speed of light, electromagnetism provides us with tools to extract the velocity of the light field oscillations. Likewise, quantum mechanics links the rapidity of electronic motion with the energy distribution of the populated quantum states. By adequately tuning the light sources, these states can be accessed by photon absorption and emission. The native scale of both the light oscillations and electron dynamics falls within the attosecond range. These elementary processes comprise the constitutional steps of any change in the physical, chemical, and biological properties of materials and soft matter. The capability of capturing and manipulating them in real-time is therefore relevant for the development of novel materials and technologies, as well as the understanding of fundamental atomic and molecular phenomena initiated by light fields [1, 2]. Since the first measurement of an attosecond pulse train (APT) [3], attosecond science has grown enormously, from the obtaining of an isolate attosecond pulse (IAP) [4] to the