Control and Optimization of High Harmonic Generation in 3D Dirac Semimetals

Abstract

3D Dirac semimetals (DSMs) are promising materials for terahertz high harmonic generation (HHG). We show that 3D DSMs' high nonlinearity opens up a regime of nonlinear optics where extreme subwavelength current density features develop within nanoscale propagation distances of the driving field. Our results reveal orders-of-magnitude enhancement in HHG intensity with thicker 3D DSM films, and show that these subwavelength features fundamentally limit HHG enhancement beyond an optimal film thickness. This decrease in HHG intensity beyond the optimal thickness constitutes an effective propagation-induced dephasing. Our findings highlight the importance of propagation dynamics in nanofilms of extreme optical nonlinearity.

1.4‐mJ High Energy Terahertz Radiation from Lithium Niobates

“…[ 11–19 ] Nevertheless, many THz science and applications are primarily focused on weak‐field passive detection of matter, based on linear light‐matter interaction process. On the other hand, intense THz field‐induced nonlinearly active control of matter is, [ 20–39 ] to some extent, still out of reach due to the shortage of highly efficient, and stable THz sources. It results in many mesoscale/microscopic physics and phenomena almost inaccessible.…”

“…It results in many mesoscale/microscopic physics and phenomena almost inaccessible. Although ultrafast microjoule‐scale THz sources have already exhibited their powerful capabilities in electron acceleration and manipulation, [ 40–45 ] field‐induced phase transition, [ 20–23 ] and nonlinear THz phenomena in a wide range of materials and structures, [ 27–34 ] the demand for millijoule‐level THz sources has not yet been fully met, especially when facing the dawn of extreme THz science overwhelmingly growing to the next frontier in nonlinear optics. [ 32,46 ]…”