Observation of Amplified Stimulated Terahertz Emission from Optically Pumped Epitaxial Graphene Heterostructures

TL;DR

This study demonstrates amplified stimulated terahertz emission from optically pumped epitaxial graphene heterostructures, revealing negative dynamic conductivity and potential for terahertz laser applications.

Contribution

It provides the first experimental evidence of amplified stimulated THz emission and negative dynamic conductivity in epitaxial graphene heterostructures.

Findings

Observation of amplified THz emission from graphene

Evidence of negative dynamic conductivity in the THz range

Correlation between pump photon spectrum and emitted THz spectrum

Abstract

We experimentally observe the fast relaxation and relatively slow recombination dynamics of photogenerated electrons/holes in an epitaxial graphene-on-Si heterostructure under pumping with a 1550-nm, 80-fs pulsed fiber laser beam and probing with the corresponding terahertz (THz) beam generated by and synchronized with the pumping laser. The time-resolved electric-field intensity originating from the coherent terahertz photon emission is electro-optically sampled in total-reflection geometry. The Fourier spectrum from 1.8 to 5.2 THz agrees well the pumping photon spectrum. This result is attributed to amplified emission of THz radiation from the graphene sample stimulated by the THz probe beam, and provides evidence for the occurrence of negative dynamic conductivity in the terahertz spectral range.