12 March 2018 Graphene in petahertz lightwave electronics

Schematic of the Experimental Setup

ICFO researchers study the instantaneous response of Dirac carriers in graphene for petahertz electronics. The speed of solid-state electronic devices, determined by the temporal dynamics of charge carriers, could potentially reach unprecedented petahertz frequencies through direct manipulation by optical fields, consisting in a million-fold increase from state-of-the-art technology. In graphene, charge carrier manipulation is facilitated by exceptionally strong coupling to optical fields, from which stems an important back-action of photoexcited carriers.

In a recent study published in Nature Communications, ICFO researchers Matthias Baudisch, Andrea Marini, Joel Cox, Francisco Silva, Stephan Teichmann and Mathieu Massicotte, led by ICREA Professors Jens Biegert, Javier Garcia de Abajo and Frank Koppens, report on the use of graphene as an ideal material for instantaneous response to ultra-fast optical fields, elucidating the role of free carriers that are created through non-linear harmonic generation.

In their investigation, the ICFO researchers focus on the ultrafast nonlinear response of graphene and the back-action onto the stimulating optical fields arising from the photo-generated free carriers at moderate pump intensity. They employed 80 fs mid infrared pulses in graphene and observed that the linear dispersion and absence of a band gap in graphene leads to an instantaneous photo-generation of free carriers by the optical field and a delayed recombination with a metal-like instantaneous response and time-dependent plasma frequency. Consequently, optical-field-driven square-wave oscillatory motion of Dirac fermions leads to the generation of new frequencies.

Finally, the simulated quantum dynamics of Dirac carriers was in excellent agreement with experimental results, thus providing the framework to describe the light field-driven dynamics of free carriers in graphene for the future development of graphene-based Petahertz optoelectronic devices.