Polarized light emission from graphene induced by terahertz pulses

TL;DR

This study demonstrates that intense terahertz pulses induce polarized spontaneous emission in graphene, revealing rapid electron momentum redistribution and providing insights into ultrafast electron dynamics.

Contribution

It presents the first experimental and theoretical analysis of terahertz-induced polarized emission in graphene, estimating electron momentum isotropization time.

Findings

Photons emitted are predominantly polarized perpendicular to the terahertz electric field.

Estimated electron momentum isotropization time is approximately 25 femtoseconds.

Reconstructed the evolution of the electron distribution function in momentum space.

Abstract

Spontaneous optical emission of graphene irradiated by intense single-cycle terahertz pulses was investigated experimentally and explained theoretically. We found that emitted photons are polarized predominantly perpendicular to the electric field of the terahertz pulse, which proves that the terahertz field not only heats the electrons, but also creates a strongly nonequilibrium momentum distribution. Comparison of the measured optical spectrum and polarization anisotropy with the results of numerical modeling allowed us to estimate a momentum isotropization time for electrons in graphene to be ~25 fs and roughly reconstruct the distribution function evolution in k-space.