Circularly polarized extreme ultraviolet high harmonic generation in graphene

TL;DR

This paper demonstrates that monolayer graphene can generate circularly polarized high harmonic radiation extending into the XUV spectral region using near-infrared lasers, advancing nanoscale ultrafast photonic applications.

Contribution

It shows for the first time that monolayer graphene can produce circularly polarized high harmonics in the XUV range driven by a single near-infrared laser, using first-principles simulations.

Findings

HHG in graphene extends to the XUV spectral region.

Circular polarization of harmonics is achieved with a single driver.

Spectra reflect graphene's six-fold symmetry.

Abstract

Circularly polarized extreme ultraviolet (XUV) radiation is highly interesting for investigation of chirality-sensitive light-matter interactions. Recent breakthroughs have enabled generation of such light sources via high harmonic generation (HHG) from rare gases. There is a growing interest in extending HHG medium from gases to solids, especially to 2D materials, as they hold great promise to develop ultra-compact solid-state photonic devices and provide insights into electronic properties of the materials themselves. However, HHG in graphene driven by terahertz to mid-infrared fields reported so far only generate low harmonic orders, and furthermore no harmonics driven by circularly polarized lasers. Here, using first-principles simulations within a time-dependent density-functional theory framework, we show that it is possible to generate HHG extending to the XUV spectral region in monolayer extended graphene excited by near-infrared lasers. Moreover, we demonstrate that a single circularly polarized driver is enough to ensure HHG in graphene with circular polarization. The corresponding spectra reflect the six-fold rotational symmetry of the graphene crystal. Extending HHG in graphene to the XUV spectral regime and realizing circular polarization represent an important step towards the development of novel nanoscale attosecond photonic devices and numerous applications such as spectroscopic investigation and nanoscale imaging of ultrafast chiral and spin dynamics in graphene and other 2D materials.