Abstract

Advancements in high harmonic generation (HHG) have led to the development of table-top XUV and soft X-ray light sources for attosecond science [1]. However, the very low conversion efficiency of HHG, particularly for longer wavelength driving laser fields [2], poses a significant practical limitation for the use of these sources in many experimental applications. We show that a two colour driving field produces a considerable enhancement of the ionization rate compared to a single colour field, leading to huge increases in the HHG efficiency. We use a tunable mid-IR (1300–1600 nm) source as a driving field and a weaker 800 nm beam as an assisting field. By systematically varying the field parameters we observe increases in HHG efficiency of over two orders of magnitude. The enhancement is achieved via subcycle control of the tunnel ionization dynamics in the bichromatic driving field.

Highlights

  • Advancements in high harmonic generation (HHG) have led to the development of table-top XUV light sources with applications ranging from ultrafast spectroscopy, X-ray science, and high resolution imaging

  • In this work we demonstrate a robust enhancement of the HHG yield purely obtained at the microscopic, single particle level [2]

  • HHG spectroscopy relies on a single particle response, mapping the dynamical properties of the interacting electronic wavefunction into the HHG spectrum

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Summary

Introduction

Advancements in high harmonic generation (HHG) have led to the development of table-top XUV light sources with applications ranging from ultrafast spectroscopy, X-ray science, and high resolution imaging. Increasing the HHG flux typically involves a careful optimization of the macroscopic aspects of the interaction via phase matching control [1]. While such approaches have successfully enhanced the HHG signal, they all share a common property – the optimization is achieved on a macroscopic level. In this work we demonstrate a robust enhancement of the HHG yield purely obtained at the microscopic, single particle level [2]. We present a microscopic scheme that defines a single, controllable parameter – namely the ionization probability – to manipulate the HHG yield, providing a robust and scalable approach to circumvent the primary bottleneck in a broad range of HHG applications

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