Extremely Nonperturbative Nonlinearities in GaAs Driven by Atomically Strong Terahertz Fields in Gold Metamaterials

TL;DR

This paper demonstrates extreme nonlinear effects in GaAs driven by intense terahertz fields from gold metamaterials, enabling ultrafast switching and nonlinear optical phenomena in the terahertz regime.

Contribution

It reveals a new regime of nonperturbative ultrafast terahertz interactions with GaAs using gold metamaterials, achieving unprecedented field strengths and nonlinear responses.

Findings

Observation of impact ionization and interband tunneling in GaAs at high terahertz fields.

Bright luminescence indicating high-density electron-hole plasma generation.

Complete switch-off of metamaterial resonance due to nonlinear effects.

Abstract

Terahertz near fields of gold metamaterials resonant at a frequency of $0.88\,\rm THz$ allow us to enter an extreme limit of non-perturbative ultrafast THz electronics: Fields reaching a ponderomotive energy in the keV range are exploited to drive nondestructive, quasi-static interband tunneling and impact ionization in undoped bulk GaAs, injecting electron-hole plasmas with densities in excess of $10^{19}\,\rm cm^{-3}$. This process causes bright luminescence at energies up to $0.5\,\rm eV$ above the band gap and induces a complete switch-off of the metamaterial resonance accompanied by self-amplitude modulation of transmitted few-cycle THz transients. Our results pave the way towards highly nonlinear THz optics and optoelectronic nanocircuitry with sub-picosecond switching times.