  The transient response of an intrinsic graphene, which is caused by the
ultrafast interband transitions, is studied theoretically for the range of
pumping correspondent to the saturated absorption regime. Spectral and temporal
dependencies of the photoexcited concentration as well as the transmission and
relitive absotption coefficients are considered for mid-IR and visible (or
near-IR) spectral regions at different durations of pulse and broadening
energies. The characteristic intencities of saturation are calculated and the
results are compared with the experimental data measured for the near-IR lasers
with a saturable absorber. The negative absorption of a probe radiation during
cascade emission of optical phonons is obtained.

Mesoscale and Nanoscale Physics;Materials Science