Femtosecond carrier dynamics and saturable absorption in graphene suspensions

TL;DR

This study investigates the ultrafast carrier relaxation and saturable absorption properties of graphene suspensions using femtosecond laser techniques, revealing two distinct relaxation times and nonlinear absorption characteristics.

Contribution

It provides new insights into the femtosecond-scale carrier dynamics and saturable absorption behavior of graphene in different solvents, using advanced ultrafast spectroscopy methods.

Findings

Graphene exhibits saturable absorption with a nonlinear coefficient of ~2 to 9x10^-8 cm/W.

Two relaxation times are identified: 130-330 fs and 3.5-4.9 ps.

Carrier relaxation involves carrier-carrier and carrier-phonon scattering processes.

Abstract

Nonlinear optical properties and carrier relaxation dynamics in graphene, suspended in three different solvents, are investigated using femtosecond (80 fs pulses) Z-scan and degenerate pumpprobe spectroscopy at 790 nm. The results demonstrate saturable absorption property of graphene with a nonlinear absorption coefficient, $beta$, of ~2 to 9x10^-8 cm/W. Two distinct time scales associated with the relaxation of photoexcited carriers, a fast one in the range of 130-330 fs (related to carrier-carrier scattering) followed by a slower one in 3.5-4.9 ps range (associated with carrier-phonon scattering) are observed.