Fluorescence of laser created electron-hole plasma in graphene

TL;DR

This paper reports the experimental observation of non-linear optical luminescence in graphene caused by high-density electron-hole plasma generated by picosecond infrared laser pulses, revealing new insights into its electronic interactions.

Contribution

It demonstrates the first observation of non-linear up- and down-converted luminescence in graphene and introduces a new method for thickness determination of multilayer flakes.

Findings

Luminescence exhibits quadratic power dependence at low laser powers.

Recombination of electron-hole pairs produces white light luminescence.

Luminescence saturation occurs at higher laser powers.

Abstract

We present an experimental observation of non-linear up- and down-converted optical luminescence of graphene and thin graphite subject to picosecond infrared laser pulses. We show that the excitation yields to a high density electron-hole plasma in graphene. It is further shown that the excited charge carries can efficiently exchange energy due to scattering in momentum space. The recombination of the resulting non-equilibrium electron-hole pairs yields to the observed white light luminescence. Due to the scattering mechanism the power dependence of the luminescence is quadratic until it saturates for higher laser power. Studying the luminescence intensity as a function of layer thickness gives further insight into its nature and provides a new tool for substrate independent thickness determination of multilayer flakes.