How to optimize high-order harmonic generation in gases

High-order harmonic generation (HHG) in gases leads to short-pulse extreme ultraviolet (XUV) radiation that is useful in a number of applications, such as attosecond science and nanoscale imaging. However, this process depends on many parameters, and there is still no consensus on how to choose the target geometry to optimize the source efficiency. We review the physics of HHG with emphasis on the macroscopic aspects of the nonlinear interaction, discussing the influence of length of medium, pressure, and intensity of the driving laser on the HHG conversion efficiency. Efficient HHG can be realized over a large range of pressures and medium lengths, if these follow a certain hyperbolic equation. This explains the large versatility in gas target designs for efficient HHG and provides design guidance for future high-flux XUV sources.

Automated summary

This article reviews the physics of high-order harmonic generation (HHG) in gases, focusing on the macroscopic aspects of the nonlinear interaction, and discusses the influence of medium length, pressure, and driving laser intensity on HHG conversion efficiency. Efficient HHG can be achieved over a wide range of pressures and medium lengths if certain hyperbolic equations are met, providing design guidance for future high-flux XUV sources.