We review recent experiments on spin excitation and manipulation in the ferromagnetic semiconductor GaMnAs. Spin
dynamics in GaMnAs have been studied by two complementary approaches - by frequency-domain techniques, such as
Brillouin light scattering (BLS) and ferromagnetic resonance (FMR); and by optical real-time techniques, such as
ultrafast pump-probe magneto-optical spectroscopy. Using BLS and FMR, magnon frequencies (or resonance fields),
were investigated as a function of Mn concentration, temperature and direction of magnetization, leading to information
on magnetic anisotropy. Time-resolved magneto-optical Kerr effect, on the other hand, was used to study photo-induced
femtosecond magnetization rotation, ultrafast optical demagnetization, and collective magnetization precession.
Optically-induced transient changes in magnetization of GaMnAs produced by femtosecond laser pulses are analyzed
and discussed in terms of the Landau-Lifshitz-Gilbert model. Finally, for completeness, we also discuss carrier-mediated
nonthermal and thermal (lattice-heating) contributions to spin dynamics.