Band structure and spin can modify the simple two-mode far-infrared sp
ectra of quantum dots. In our investigation of these effects we start
from a k.p Hamiltonian for the conduction, valence, and spin-orbit spl
it-off bands, with potentials for subband formation and harmonic later
al confinement. Taking into account the nonparabolicity of the conduct
ion band and spin-orbit coupling due to the confining potentials, we c
alculate the dipole excitation spectra of quantum dots on InSb with on
e and two electrons. Spin-orbit coupling leads to a level anticrossing
in the omega- mode and nonparabolicity modifies the omega+ mode demon
strating violation of Kohn's theorem.