THz emission from multiple ionized plasma

TL;DR

This paper develops a photocurrent model for high-intensity laser-driven plasma THz generation, explaining experimental results and achieving over 0.2 mJ THz pulses with high efficiency.

Contribution

It introduces a new model accounting for high-ionization states, enhancing understanding of THz generation mechanisms at high laser intensities.

Findings

Achieved 0.2 mJ THz pulses experimentally.

Demonstrated high conversion efficiency over 1%.

Model aligns well with observed spectral and temporal data.

Abstract

Studies employing nonlinear interactions of THz pulses are nowadays a promising scientific research field. To capture these phenomena, THz pulses with energy ranging from hundreds of \muJ to the mJ level are necessary. However, techniques that provide pulses with such energy levels are still not widely established. Upscaling methods of laser-solid interaction is limited by the damage threshold of materials, while the mechanism of THz generation from high intensity laser-gas interactions is not fully understood yet. Here, we establish the photocurrent model of laser-driven plasma THz generation in the high-intensity regime by accounting for high-ionization states of the target gas. Our model shows excellent agreement with experimental observations, provides a clear explanation of phenomena in both spectral and temporal domains, and explains the high conversion efficiency from laser to THz. In the experiments, we achieved a generation of 0.2 mJ THz pulses, driven by a Ti:sapphire laser with a conversion efficiency exceeding 1 %.