  We present scanning optical stroboscopic confocal microscopy and spectroscopy
measurements wherein three degrees of freedom, namely energy, real-space, and
real-time, are resolvable. The edge-state propagation is detected as a temporal
change in the optical response in the downstream edge. We succeeded in
visualizing the excited states of the most fundamental fractional quantum Hall
(FQH) state and the collective excitations near the edge. The results verify
the current understanding of the edge excitation and also point toward further
dynamics outside the edge channel.
