Boosting terahertz generation in laser-field ionized gases using a sawtooth wave shape

TL;DR

This paper demonstrates that using a specially shaped sawtooth waveform generated by multicolor laser pulses significantly enhances terahertz wave production in laser-ionized gases, achieving unprecedented efficiency levels.

Contribution

It introduces a novel waveform shaping technique with multicolor pulses to optimize free electron trajectories for improved THz generation in gases.

Findings

THz conversion efficiency reaches percent level

Analytical and 3D simulations confirm waveform optimization benefits

Multicolor pulse design significantly enhances tunnel ionization-based THz generation

Abstract

Broadband ultrashort terahertz (THz) pulses can be produced using plasma generation in a noble gas ionized by femtosecond two-color pulses. Here we demonstrate that, by using multiple-frequency laser pulses, one can obtain a waveform which optimizes the free electron trajectories in such a way that they reach the highest velocity at the electric field extrema. This allows to increase the THz conversion efficiency to the percent level, an unprecedented performance for THz generation in gases. Besides the analytical study of THz generation using a local current model, we perform comprehensive 3D simulations accounting for propagation effects which confirm this prediction. Our results show that THz conversion via tunnel ionization can be greatly improved with well-designed multicolor pulses.