  In this paper, we investigate the propagation of the light pulse reflected
from the layer system with a graphene layer. We show a tunable transition
between positive and negative group delay of the optical pulse reflection in
such a layered system controlled by the properties of the graphene layer, and
reveal two mechanisms to control the propagation properties of the light
reflected from such systems. It is demonstrated that the reflected group delays
are greatly tunable from positive and negative values in both mechanisms of
resonances and the excitations of the surface plasmon resonances, which are
adjusted by tuning the Fermi energy and temperature of the graphene layer. Our
results are helpful to control the pulse propagations and are useful for design
of graphene-based optical devices.
