  We propose a strategy that uses a tunable laser and an alternating non-linear
potential to sort a suspension of assorted semiconducting nanotubes. Since, a
polarized exciton is a dipole, the excited nanotubes will experience a net
force and may then diffuse towards an electrode. The calculated exciton binding
energy suddenly drops to zero and the force on the nanotube increases
dramatically when the exciton disassociates as the nanotube moves towards the
electrode. The quantum adiabatic theorem shows that excitons will be polarized
for potential frequencies typical for experiments $\approx 10$ MHz.
