  This paper is relevant to the recent optical transmission experiments of
Karrai et al. for vortices in high Tc superconductors. We begin with a
substantial review and introduction. The microscopic response of vortices is
calculated from the Bogoliubov-deGennes equation, including an equation of
motion and conductivity. We find that the expected resonant dipole transtition
is not present because of translation invariance. We consider the effect of
pinning and show that in the presence of pinning one recovers the dipole
resonance. Thus we conclude that pinning may play an important role in the
experiment.
