Pulse shaping in the terahertz frequency range for the control of photo-excited carriers in graphene

TL;DR

This paper demonstrates theoretically that pulse shaping of terahertz laser pulses can control carrier populations in graphene, enabling modulation of carrier density and multi-photon processes through spectral optimization.

Contribution

It introduces a spectral parametrization using B-splines and applies differential evolution to optimize pulse shapes for controlling carriers in graphene.

Findings

Carrier density can be changed by a factor of 4 with fixed pulse energy.

Selective suppression or enhancement of multi-photon absorption is achievable.

Pulse shaping influences scattering mechanisms in graphene.

Abstract

The shape of a few-cycle terahertz (THz) laser pulse can be optimized to provide control over conduction band populations in graphene. To demonstrate this control in a theoretical way, a spectral parametrization of the driving pulse using $B$-splines is used in order to obtain experimentally realistic pulses of bandwidth $\sim$ 30 THz. Optimization of the spectral shape is performed via differential evolution, using the $B$-splines expansion coefficients as decision variables. Numerical results show the possibility of changing the carrier density in graphene by a factor of 4 for a fixed pulse energy. In addition, we show that it is possible to selectively suppress or enhance multi-photon absorption features by optimizing over narrow windows in reciprocal space. The application of pulse shaping to the control of scattering mechanisms in graphene is also discussed.