  Electric dipole ($E1$) response of $^{6}$He is studied with a fully
microscopic six-body calculation. The wave functions for the ground and excited
states are expressed as a superposition of explicitly correlated Gaussians
(CG). Final state interactions of three-body decay channels are explicitly
taken into account. The ground state properties and the low-energy $E1$
strength are obtained consistently with observations. Two main peaks as well as
several small peaks are found in the $E1$ strength function. The peak at the
high-energy region indicates a typical macroscopic picture of the giant dipole
resonance, the out-of-phase proton-neutron motion. The transition densities of
the lower-lying peaks exhibit in-phase proton-neutron motion in the internal
region, out-of-phase motion near the surface region, and spatially extended
neutron oscillation, indicating a soft-dipole mode (SDM) and its vibrationally
excited mode.
